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/app.html

@@ -4,6 +4,12 @@
 		<meta charset="utf-8" />
 		<link rel="icon" href="%sveltekit.assets%/favicon.png" />
 		<meta name="viewport" content="width=device-width, initial-scale=1" />
+		<link rel="manifest" href="%sveltekit.assets%/manifest.json" />
+		<meta name="theme-color" content="#6366f1" />
+		<meta name="apple-mobile-web-app-capable" content="yes" />
+		<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />
+		<meta name="apple-mobile-web-app-title" content="Launcher" />
+		<link rel="apple-touch-icon" href="%sveltekit.assets%/icon.svg" />
 		<script>
 			// Inline script to prevent FOUC — set theme class before first paint
 			(function () {