feat(auth): admin invite links

Replaces the blunt registrationEnabled toggle with per-invite access.
Invites are tokenized, single-use, optionally locked to an email, can
grant user or admin role, and expire (default 7d, max 90d).

- Invite model with tokenHash (bcrypt), email, role, expiresAt,
  usedAt/usedByUserId.
- inviteService: create, list, revoke, findInviteByToken, consumeInvite.
  Token is shown exactly once at creation.
- /admin/invites page: list with status (Active/Used/Expired), generate
  with email lock + role + custom expiry, copy one-shot URL, revoke.
- /register?invite=TOKEN: accepts invite even when registrationEnabled
  is false; shows a banner; enforces email lock; applies the invite's
  role on creation; consumes the invite on success.
- Linked from the admin navbar.

src/lib/server/services/inviteService.ts

@@ -0,0 +1,100 @@
+import bcrypt from 'bcryptjs';
+import { prisma } from '../prisma.js';
+
+const SALT_ROUNDS = 12;
+const DEFAULT_EXPIRY_DAYS = 7;
+
+export interface CreateInviteInput {
+	readonly email?: string;
+	readonly role?: 'user' | 'admin';
+	readonly expiresInDays?: number;
+	readonly createdById?: string;
+}
+
+export interface IssuedInvite {
+	readonly id: string;
+	readonly token: string; // raw token — shown to admin exactly once
+	readonly email: string | null;
+	readonly role: string;
+	readonly expiresAt: Date;
+}
+
+function generateToken(): string {
+	const bytes = new Uint8Array(32);
+	crypto.getRandomValues(bytes);
+	return Array.from(bytes, (b) => b.toString(16).padStart(2, '0')).join('');
+}
+
+export async function createInvite(input: CreateInviteInput): Promise<IssuedInvite> {
+	const token = generateToken();
+	const tokenHash = await bcrypt.hash(token, SALT_ROUNDS);
+	const days = input.expiresInDays ?? DEFAULT_EXPIRY_DAYS;
+	const expiresAt = new Date();
+	expiresAt.setDate(expiresAt.getDate() + days);
+
+	const invite = await prisma.invite.create({
+		data: {
+			tokenHash,
+			email: input.email ?? null,
+			role: input.role ?? 'user',
+			expiresAt,
+			createdById: input.createdById ?? null
+		}
+	});
+
+	return {
+		id: invite.id,
+		token,
+		email: invite.email,
+		role: invite.role,
+		expiresAt: invite.expiresAt
+	};
+}
+
+export async function listInvites() {
+	return prisma.invite.findMany({
+		orderBy: { createdAt: 'desc' },
+		select: {
+			id: true,
+			email: true,
+			role: true,
+			expiresAt: true,
+			usedAt: true,
+			usedByUserId: true,
+			createdById: true,
+			createdAt: true
+		}
+	});
+}
+
+export async function revokeInvite(id: string): Promise<void> {
+	await prisma.invite.deleteMany({ where: { id } });
+}
+
+/**
+ * Look up an invite by raw token. Performs a full table scan of non-expired,
+ * non-used invites and bcrypt-compares each. Invite volume is tiny in practice,
+ * so the scan cost is negligible.
+ */
+export async function findInviteByToken(token: string) {
+	const candidates = await prisma.invite.findMany({
+		where: {
+			usedAt: null,
+			expiresAt: { gt: new Date() }
+		}
+	});
+
+	for (const invite of candidates) {
+		if (await bcrypt.compare(token, invite.tokenHash)) {
+			return invite;
+		}
+	}
+	return null;
+}
+
+export async function consumeInvite(inviteId: string, userId: string): Promise<void> {
+	await prisma.invite.update({
+		where: { id: inviteId },
+		data: { usedAt: new Date(), usedByUserId: userId }
+	});
+}

src/routes/admin/+layout.svelte

@@ -8,6 +8,7 @@
 
 	const navItems = $derived([
 		{ href: '/admin/users', labelKey: 'admin.users' },
+		{ href: '/admin/invites', label: 'Invites' },
 		{ href: '/admin/groups', labelKey: 'admin.groups' },
 		{ href: '/admin/tags', label: 'Tags' },
 		{ href: '/admin/audit-log', label: 'Audit Log' },

src/routes/admin/invites/+page.server.ts

@@ -0,0 +1,9 @@
+import type { PageServerLoad } from './$types.js';
+import { requireAdmin } from '$lib/server/middleware/authorize.js';
+import * as inviteService from '$lib/server/services/inviteService.js';
+
+export const load: PageServerLoad = async (event) => {
+	requireAdmin(event);
+	const invites = await inviteService.listInvites();
+	return { invites };
+};

src/routes/admin/invites/+page.svelte

@@ -0,0 +1,257 @@
+<script lang="ts">
+	import { invalidateAll } from '$app/navigation';
+	import type { PageData } from './$types.js';
+
+	let { data }: { data: PageData } = $props();
+
+	let showForm = $state(false);
+	let creating = $state(false);
+	let err = $state<string | null>(null);
+
+	let email = $state('');
+	let role = $state<'user' | 'admin'>('user');
+	let expiresInDays = $state(7);
+
+	let createdUrl = $state<string | null>(null);
+
+	async function submit(evt: SubmitEvent) {
+		evt.preventDefault();
+		err = null;
+		creating = true;
+		try {
+			const res = await fetch('/api/admin/invites', {
+				method: 'POST',
+				headers: { 'Content-Type': 'application/json' },
+				body: JSON.stringify({
+					email: email || undefined,
+					role,
+					expiresInDays
+				})
+			});
+			const json = await res.json();
+			if (!json.success) {
+				err = json.error ?? 'Failed to create invite';
+				return;
+			}
+			createdUrl = json.data.url;
+			email = '';
+			role = 'user';
+			expiresInDays = 7;
+			showForm = false;
+			await invalidateAll();
+		} catch {
+			err = 'Failed to create invite';
+		} finally {
+			creating = false;
+		}
+	}
+
+	async function revoke(id: string) {
+		err = null;
+		try {
+			const res = await fetch(`/api/admin/invites/${id}`, { method: 'DELETE' });
+			const json = await res.json();
+			if (!json.success) {
+				err = json.error ?? 'Failed to revoke invite';
+				return;
+			}
+			await invalidateAll();
+		} catch {
+			err = 'Failed to revoke invite';
+		}
+	}
+
+	async function copyUrl(url: string) {
+		try {
+			await navigator.clipboard.writeText(url);
+		} catch {
+			/* ignore */
+		}
+	}
+
+	function fmt(d: string | Date | null): string {
+		if (!d) return '—';
+		return new Date(d).toLocaleString();
+	}
+
+	function inviteStatus(inv: { usedAt: Date | string | null; expiresAt: Date | string }): string {
+		if (inv.usedAt) return 'Used';
+		if (new Date(inv.expiresAt) < new Date()) return 'Expired';
+		return 'Active';
+	}
+</script>
+
+<svelte:head>
+	<title>Invites</title>
+</svelte:head>
+
+<div class="mx-auto max-w-4xl space-y-6 px-4 py-8">
+	<div class="flex items-center justify-between">
+		<div>
+			<h1 class="text-2xl font-bold text-foreground">Invites</h1>
+			<p class="mt-1 text-sm text-muted-foreground">
+				Generate invite links so people can register even when public registration is disabled.
+			</p>
+		</div>
+		{#if !showForm}
+			<button
+				type="button"
+				onclick={() => (showForm = true)}
+				class="rounded-md bg-primary px-4 py-2 text-sm font-medium text-primary-foreground hover:bg-primary/90"
+			>
+				Generate invite
+			</button>
+		{/if}
+	</div>
+
+	{#if err}
+		<div class="rounded-lg border border-destructive/50 bg-destructive/10 p-3 text-sm text-destructive">
+			{err}
+		</div>
+	{/if}
+
+	{#if createdUrl}
+		<div class="rounded-lg border border-yellow-500/50 bg-yellow-500/10 p-4">
+			<h3 class="mb-1 text-sm font-semibold text-foreground">Invite created</h3>
+			<p class="mb-3 text-xs text-muted-foreground">
+				Share this link with the recipient. It will only be shown once.
+			</p>
+			<div class="flex items-center gap-2">
+				<code
+					class="flex-1 truncate rounded-md border border-input bg-background px-3 py-2 text-xs font-mono text-foreground"
+				>
+					{createdUrl}
+				</code>
+				<button
+					type="button"
+					onclick={() => createdUrl && copyUrl(createdUrl)}
+					class="rounded-md bg-primary px-3 py-2 text-xs font-medium text-primary-foreground hover:bg-primary/90"
+				>
+					Copy
+				</button>
+			</div>
+			<button
+				type="button"
+				onclick={() => (createdUrl = null)}
+				class="mt-3 text-xs text-muted-foreground hover:text-foreground"
+			>
+				I have copied the link
+			</button>
+		</div>
+	{/if}
+
+	{#if showForm}
+		<form
+			onsubmit={submit}
+			class="space-y-4 rounded-xl border border-border bg-card p-5"
+		>
+			<div>
+				<label for="inv-email" class="mb-1 block text-sm font-medium text-card-foreground">
+					Email <span class="text-xs font-normal text-muted-foreground">(optional — locks invite to one email)</span>
+				</label>
+				<input
+					id="inv-email"
+					type="email"
+					bind:value={email}
+					placeholder="jane@example.com"
+					class="w-full rounded-lg border border-input bg-background px-3 py-2 text-sm text-foreground"
+				/>
+			</div>
+			<div class="grid grid-cols-2 gap-4">
+				<div>
+					<label for="inv-role" class="mb-1 block text-sm font-medium text-card-foreground">Role</label>
+					<select
+						id="inv-role"
+						bind:value={role}
+						class="w-full rounded-lg border border-input bg-background px-3 py-2 text-sm text-foreground"
+					>
+						<option value="user">User</option>
+						<option value="admin">Admin</option>
+					</select>
+				</div>
+				<div>
+					<label for="inv-expiry" class="mb-1 block text-sm font-medium text-card-foreground">
+						Expires in (days)
+					</label>
+					<input
+						id="inv-expiry"
+						type="number"
+						min="1"
+						max="90"
+						bind:value={expiresInDays}
+						class="w-full rounded-lg border border-input bg-background px-3 py-2 text-sm text-foreground"
+					/>
+				</div>
+			</div>
+			<div class="flex justify-end gap-2">
+				<button
+					type="button"
+					onclick={() => (showForm = false)}
+					class="rounded-md border border-border px-3 py-2 text-sm text-foreground hover:bg-muted"
+				>
+					Cancel
+				</button>
+				<button
+					type="submit"
+					disabled={creating}
+					class="rounded-md bg-primary px-4 py-2 text-sm font-medium text-primary-foreground hover:bg-primary/90 disabled:opacity-50"
+				>
+					{creating ? 'Creating…' : 'Create invite'}
+				</button>
+			</div>
+		</form>
+	{/if}
+
+	<div class="overflow-hidden rounded-xl border border-border bg-card">
+		<table class="w-full text-sm">
+			<thead class="bg-muted/40 text-xs uppercase tracking-wide text-muted-foreground">
+				<tr>
+					<th class="px-4 py-3 text-left font-medium">Email</th>
+					<th class="px-4 py-3 text-left font-medium">Role</th>
+					<th class="px-4 py-3 text-left font-medium">Status</th>
+					<th class="px-4 py-3 text-left font-medium">Expires</th>
+					<th class="px-4 py-3 text-left font-medium">Created</th>
+					<th class="px-4 py-3"></th>
+				</tr>
+			</thead>
+			<tbody>
+				{#each data.invites as inv (inv.id)}
+					{@const status = inviteStatus(inv)}
+					<tr class="border-t border-border">
+						<td class="px-4 py-3 text-card-foreground">{inv.email ?? '—'}</td>
+						<td class="px-4 py-3 text-card-foreground">{inv.role}</td>
+						<td class="px-4 py-3">
+							<span
+								class="rounded-full px-2 py-0.5 text-xs {status === 'Active'
+									? 'bg-emerald-500/15 text-emerald-500'
+									: status === 'Used'
+										? 'bg-muted text-muted-foreground'
+										: 'bg-destructive/15 text-destructive'}"
+							>
+								{status}
+							</span>
+						</td>
+						<td class="px-4 py-3 text-muted-foreground">{fmt(inv.expiresAt)}</td>
+						<td class="px-4 py-3 text-muted-foreground">{fmt(inv.createdAt)}</td>
+						<td class="px-4 py-3 text-right">
+							<button
+								type="button"
+								onclick={() => revoke(inv.id)}
+								class="text-xs text-destructive hover:underline"
+							>
+								Revoke
+							</button>
+						</td>
+					</tr>
+				{/each}
+				{#if data.invites.length === 0}
+					<tr>
+						<td colspan="6" class="px-4 py-6 text-center text-sm text-muted-foreground">
+							No invites yet.
+						</td>
+					</tr>
+				{/if}
+			</tbody>
+		</table>
+	</div>
+</div>

src/routes/api/admin/invites/+server.ts

@@ -0,0 +1,60 @@
+import { json } from '@sveltejs/kit';
+import type { RequestHandler } from './$types.js';
+import { z } from 'zod';
+import { requireAdmin } from '$lib/server/middleware/authorize.js';
+import { success, error } from '$lib/server/utils/response.js';
+import * as inviteService from '$lib/server/services/inviteService.js';
+
+const createInviteSchema = z.object({
+	email: z.string().email().optional(),
+	role: z.enum(['user', 'admin']).optional(),
+	expiresInDays: z.number().int().min(1).max(90).optional()
+});
+
+export const GET: RequestHandler = async (event) => {
+	requireAdmin(event);
+	const invites = await inviteService.listInvites();
+	return json(success(invites));
+};
+
+export const POST: RequestHandler = async (event) => {
+	const admin = requireAdmin(event);
+
+	let body: unknown;
+	try {
+		body = await event.request.json();
+	} catch {
+		body = {};
+	}
+
+	const parsed = createInviteSchema.safeParse(body);
+	if (!parsed.success) {
+		const msg = parsed.error.errors.map((e) => e.message).join(', ');
+		return json(error(msg), { status: 400 });
+	}
+
+	try {
+		const invite = await inviteService.createInvite({
+			...parsed.data,
+			createdById: admin.id
+		});
+
+		const origin = event.request.headers.get('origin') ?? event.url.origin;
+		const inviteUrl = `${origin}/register?invite=${invite.token}`;
+
+		return json(
+			success({
+				id: invite.id,
+				email: invite.email,
+				role: invite.role,
+				expiresAt: invite.expiresAt,
+				token: invite.token,
+				url: inviteUrl
+			}),
+			{ status: 201 }
+		);
+	} catch (err) {
+		const message = err instanceof Error ? err.message : 'Failed to create invite';
+		return json(error(message), { status: 500 });
+	}
+};

src/routes/api/admin/invites/[id]/+server.ts

@@ -0,0 +1,19 @@
+import { json } from '@sveltejs/kit';
+import type { RequestHandler } from './$types.js';
+import { requireAdmin } from '$lib/server/middleware/authorize.js';
+import { success, error } from '$lib/server/utils/response.js';
+import * as inviteService from '$lib/server/services/inviteService.js';
+
+export const DELETE: RequestHandler = async (event) => {
+	requireAdmin(event);
+	const id = event.params.id;
+	if (!id) return json(error('Invite id required'), { status: 400 });
+
+	try {
+		await inviteService.revokeInvite(id);
+		return json(success({ revoked: true }));
+	} catch (err) {
+		const message = err instanceof Error ? err.message : 'Failed to revoke invite';
+		return json(error(message), { status: 500 });
+	}
+};

src/routes/register/+page.server.ts

@@ -6,6 +6,7 @@ import { registerSchema } from '$lib/utils/validators.js';
 import { prisma } from '$lib/server/prisma.js';
 import * as userService from '$lib/server/services/userService.js';
 import * as groupService from '$lib/server/services/groupService.js';
+import * as inviteService from '$lib/server/services/inviteService.js';
 import { issueSessionCookies } from '$lib/server/utils/sessionCookies.js';
 import { DEFAULTS } from '$lib/utils/constants.js';
 
@@ -17,26 +18,43 @@ async function isRegistrationEnabled(): Promise<boolean> {
 	return settings?.registrationEnabled ?? true;
 }
 
-export const load: PageServerLoad = async ({ locals }) => {
-	// If already logged in, redirect to home
+export const load: PageServerLoad = async ({ locals, url }) => {
 	if (locals.user) {
 		throw redirect(302, '/');
 	}
 
+	const inviteToken = url.searchParams.get('invite');
+	const invite = inviteToken ? await inviteService.findInviteByToken(inviteToken) : null;
+
 	const registrationEnabled = await isRegistrationEnabled();
-	if (!registrationEnabled) {
+	if (!registrationEnabled && !invite) {
 		throw error(403, { message: 'Registration is currently disabled' });
 	}
 
 	const form = await superValidate(zod(registerSchema));
-	return { form, registrationEnabled };
+	if (invite?.email) {
+		form.data.email = invite.email;
+	}
+
+	return {
+		form,
+		registrationEnabled,
+		invite: invite
+			? { lockedEmail: invite.email, role: invite.role, expiresAt: invite.expiresAt }
+			: null,
+		inviteToken: invite ? inviteToken : null
+	};
 };
 
 export const actions: Actions = {
 	default: async (event) => {
-		const { request, cookies } = event;
+		const { request, cookies, url } = event;
+
+		const inviteToken = url.searchParams.get('invite');
+		const invite = inviteToken ? await inviteService.findInviteByToken(inviteToken) : null;
+
 		const registrationEnabled = await isRegistrationEnabled();
-		if (!registrationEnabled) {
+		if (!registrationEnabled && !invite) {
 			throw error(403, { message: 'Registration is currently disabled' });
 		}
 
@@ -48,24 +66,30 @@ export const actions: Actions = {
 
 		const { email, password, displayName } = form.data;
 
-		// Check email uniqueness
+		// If the invite locks an email, enforce it
+		if (invite?.email && invite.email.toLowerCase() !== email.toLowerCase()) {
+			return setError(form, 'email', 'This invite is locked to a different email');
+		}
+
 		const existingUser = await userService.findByEmail(email);
 		if (existingUser) {
 			return setError(form, 'email', 'An account with this email already exists');
 		}
 
-		// Create user
 		const user = await userService.create({
 			email,
 			password,
 			displayName,
 			authProvider: 'local',
-			role: 'user'
+			role: invite?.role === 'admin' ? 'admin' : 'user'
 		});
 
-		// Add user to default groups
 		await groupService.addUserToDefaultGroups(user.id);
 
+		if (invite) {
+			await inviteService.consumeInvite(invite.id, user.id);
+		}
+
 		await issueSessionCookies(cookies, user, { event });
 
 		throw redirect(302, '/');

src/routes/register/+page.svelte

@@ -39,6 +39,18 @@
 			<p class="mt-1 text-sm text-muted-foreground">{$t('auth.register_subtitle')}</p>
 		</div>
 
+		{#if data.invite}
+			<div class="mb-4 rounded-lg border border-primary/40 bg-primary/10 p-3 text-xs text-foreground">
+				You have been invited to join
+				{#if data.invite.role === 'admin'}
+					as an <span class="font-semibold">administrator</span>
+				{/if}.
+				{#if data.invite.lockedEmail}
+					This invite is locked to <span class="font-mono">{data.invite.lockedEmail}</span>.
+				{/if}
+			</div>
+		{/if}
+
 		<form method="POST" use:enhance class="space-y-4">
 			<div>
 				<label for="displayName" class="mb-1 block text-sm font-medium text-card-foreground">
@@ -67,8 +79,9 @@
 					name="email"
 					type="email"
 					autocomplete="email"
+					readonly={!!data.invite?.lockedEmail}
 					bind:value={$form.email}
-					class="w-full rounded-lg border border-input bg-background px-3 py-2.5 text-sm text-foreground placeholder:text-muted-foreground transition-colors focus:border-primary focus:outline-none focus:ring-2 focus:ring-ring/30"
+					class="w-full rounded-lg border border-input bg-background px-3 py-2.5 text-sm text-foreground placeholder:text-muted-foreground transition-colors focus:border-primary focus:outline-none focus:ring-2 focus:ring-ring/30 read-only:opacity-70"
 					placeholder={$t('auth.email_placeholder')}
 				/>
 				{#if $errors.email}