feat: offline save-for-later + background sync for mark-cooked (v0.65.0)

Adds a "Save offline" button on the recipe page that force-refetches
the current page so the service worker's cache picks up a fresh copy
right now, plus a small IndexedDB-backed list (lib/offline-db.ts) of
what's been saved. The /offline fallback page now reads that list and
renders it instead of being a dead end with just a "go back" link.

Also fixes the service worker's network-first fetch handler, which
never wrote successful responses into its cache -- meaning the
existing offline page's claim that "recently visited recipes are
available" was never actually true. It populates the cache on every
successful GET now.

Background sync: marking a batch-cook dish as cooked while offline
(the only existing mark-cooked call site in the app) now queues the
request in IndexedDB instead of just failing, and registers a
Background Sync (public/sw.js's "sync" listener replays the queue)
for Chromium; lib/offline-queue.ts's online-event fallback covers
Safari/Firefox, which never fire that event at all. Both replay paths
read/write the same IndexedDB store so either one drains it.

Also removes apps/web/public/manifest.json, a stale static manifest
that layout.tsx used to link to before the previous commit pointed it
at the real generated route (app/manifest.ts) -- it had gone
unnoticed and unused since.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/app/layout.tsx

@@ -6,6 +6,7 @@ import { auth } from "@/lib/auth/server";
 import type { Locale } from "@/lib/i18n/provider";
 import { SwRegister } from "@/components/pwa/sw-register";
 import { InstallPrompt } from "@/components/pwa/install-prompt";
+import { OfflineSyncManager } from "@/components/pwa/offline-sync-manager";
 import { getMarketingLocale } from "@/lib/marketing-locale";
 import "./globals.css";
 
@@ -59,6 +60,7 @@ export default async function RootLayout({
         <Providers initialLocale={initialLocale}>{children}</Providers>
         <SwRegister />
         <InstallPrompt />
+        <OfflineSyncManager />
       </body>
     </html>
   );