Add SvelteKit frontend with Tailwind CSS (Phase 4)

Build a modern, calm web UI using SvelteKit 5 + Tailwind CSS v4.

Pages:
- Setup wizard (first-run admin account creation)
- Login with JWT token management and auto-refresh
- Dashboard with stats cards and recent events timeline
- Servers: add/delete Immich server connections with validation
- Trackers: create album trackers with album picker, event type
  selection, target assignment, and scan interval config
- Templates: Jinja2 message template editor with live preview
- Targets: Telegram and webhook notification targets with test
- Users: admin-only user management (create/delete)

Architecture:
- Reactive auth state with Svelte 5 runes
- API client with JWT auth, auto-refresh on 401
- Static adapter builds to 153KB for embedding in FastAPI
- Vite proxy config for dev server -> backend API
- Sidebar layout with navigation and user info

Also adds Rule 2 to primary plan: perform detailed code review
after completing each phase.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/routes/login/+page.svelte

@@ -0,0 +1,74 @@
+<script lang="ts">
+	import { goto } from '$app/navigation';
+	import { onMount } from 'svelte';
+	import { api } from '$lib/api';
+	import { login } from '$lib/auth.svelte';
+
+	let username = $state('');
+	let password = $state('');
+	let error = $state('');
+	let submitting = $state(false);
+
+	onMount(async () => {
+		try {
+			const res = await api<{ needs_setup: boolean }>('/auth/needs-setup');
+			if (res.needs_setup) goto('/setup');
+		} catch { /* ignore */ }
+	});
+
+	async function handleSubmit(e: SubmitEvent) {
+		e.preventDefault();
+		error = '';
+		submitting = true;
+		try {
+			await login(username, password);
+			goto('/');
+		} catch (err: any) {
+			error = err.message || 'Login failed';
+		}
+		submitting = false;
+	}
+</script>
+
+<div class="min-h-screen flex items-center justify-center bg-[var(--color-background)]">
+	<div class="w-full max-w-sm">
+		<div class="bg-[var(--color-card)] border border-[var(--color-border)] rounded-lg p-6 shadow-sm">
+			<h1 class="text-xl font-semibold text-center mb-1">Immich Watcher</h1>
+			<p class="text-sm text-[var(--color-muted-foreground)] text-center mb-6">Sign in to your account</p>
+
+			{#if error}
+				<div class="bg-red-50 text-red-700 text-sm rounded-md p-3 mb-4">{error}</div>
+			{/if}
+
+			<form onsubmit={handleSubmit} class="space-y-4">
+				<div>
+					<label for="username" class="block text-sm font-medium mb-1.5">Username</label>
+					<input
+						id="username"
+						type="text"
+						bind:value={username}
+						required
+						class="w-full px-3 py-2 border border-[var(--color-border)] rounded-md text-sm focus:outline-none focus:ring-2 focus:ring-[var(--color-primary)] bg-[var(--color-background)]"
+					/>
+				</div>
+				<div>
+					<label for="password" class="block text-sm font-medium mb-1.5">Password</label>
+					<input
+						id="password"
+						type="password"
+						bind:value={password}
+						required
+						class="w-full px-3 py-2 border border-[var(--color-border)] rounded-md text-sm focus:outline-none focus:ring-2 focus:ring-[var(--color-primary)] bg-[var(--color-background)]"
+					/>
+				</div>
+				<button
+					type="submit"
+					disabled={submitting}
+					class="w-full py-2 px-4 bg-[var(--color-primary)] text-[var(--color-primary-foreground)] rounded-md text-sm font-medium hover:opacity-90 transition-opacity disabled:opacity-50"
+				>
+					{submitting ? 'Signing in...' : 'Sign in'}
+				</button>
+			</form>
+		</div>
+	</div>
+</div>