feat(phase3): PWA, auto-discovery, bookmarklet, multi-tab sync

- PWA: manifest, service worker (cache-first static, network-first API),
  offline page, install prompt banner
- Auto-discovery: Docker socket + Traefik API scanning, approval UI
- Quick-add bookmarklet: popup-based add page, favicon auto-detect
- Multi-tab sync: BroadcastChannel for theme + data changes
- i18n translations for all new strings (EN/RU)

src/routes/api/apps/quick-add/+server.ts

@@ -0,0 +1,71 @@
+import { json } from '@sveltejs/kit';
+import type { RequestHandler } from './$types';
+import { requireAuth } from '$lib/server/middleware/authenticate.js';
+import * as appService from '$lib/server/services/appService.js';
+import { success, error } from '$lib/server/utils/response.js';
+import { z } from 'zod';
+
+const quickAddSchema = z.object({
+	url: z
+		.string()
+		.url('Invalid URL')
+		.refine(
+			(u) => u.startsWith('http://') || u.startsWith('https://'),
+			'URL must use http or https protocol'
+		),
+	name: z.string().min(1, 'Name is required').max(200),
+	description: z.string().max(1000).optional()
+});
+
+/**
+ * POST /api/apps/quick-add — Quick-add an app with sensible defaults.
+ * Accepts { url, name, description? }, creates app with healthcheck enabled
+ * and attempts to auto-detect a favicon icon from the URL's domain.
+ */
+export const POST: RequestHandler = async (event) => {
+	const user = requireAuth(event);
+
+	let body: unknown;
+	try {
+		body = await event.request.json();
+	} catch {
+		return json(error('Invalid JSON body'), { status: 400 });
+	}
+
+	const parsed = quickAddSchema.safeParse(body);
+	if (!parsed.success) {
+		const messages = parsed.error.errors.map((e) => e.message).join(', ');
+		return json(error(messages), { status: 400 });
+	}
+
+	const { url, name, description } = parsed.data;
+
+	// Attempt to derive a favicon URL from the domain
+	let faviconUrl: string | undefined;
+	try {
+		const parsedUrl = new URL(url);
+		faviconUrl = `${parsedUrl.origin}/favicon.ico`;
+	} catch {
+		// URL parsing failed — skip icon detection
+	}
+
+	try {
+		const app = await appService.create({
+			name,
+			url,
+			description,
+			icon: faviconUrl,
+			iconType: faviconUrl ? 'url' : 'lucide',
+			healthcheckEnabled: true,
+			healthcheckInterval: 300,
+			healthcheckMethod: 'GET',
+			healthcheckExpectedStatus: 200,
+			healthcheckTimeout: 5000,
+			createdById: user.id
+		});
+		return json(success(app), { status: 201 });
+	} catch (err) {
+		const message = err instanceof Error ? err.message : 'Failed to create app';
+		return json(error(message), { status: 500 });
+	}
+};