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/components/recipe/save-offline-button.tsx

@@ -0,0 +1,49 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import { usePathname } from "next/navigation";
+import { toast } from "sonner";
+import { Download, Check } from "lucide-react";
+import { Button } from "@/components/ui/button";
+import { isRecipeSavedOffline, saveRecipeOffline, unsaveRecipeOffline } from "@/lib/offline-db";
+
+export function SaveOfflineButton({ recipeId, recipeTitle }: { recipeId: string; recipeTitle: string }) {
+  const pathname = usePathname();
+  const [saved, setSaved] = useState(false);
+  const [busy, setBusy] = useState(false);
+
+  useEffect(() => {
+    isRecipeSavedOffline(recipeId).then(setSaved).catch(() => {});
+  }, [recipeId]);
+
+  async function toggle() {
+    setBusy(true);
+    try {
+      if (saved) {
+        await unsaveRecipeOffline(recipeId);
+        setSaved(false);
+        toast.success("Removed from offline recipes");
+        return;
+      }
+      // Re-fetching the current page (rather than relying on the visit that
+      // already happened) forces the service worker's fetch handler to pin
+      // a fresh copy in its cache right now, regardless of how the normal
+      // cache eviction/versioning plays out later.
+      await fetch(pathname, { cache: "reload" });
+      await saveRecipeOffline(recipeId, recipeTitle);
+      setSaved(true);
+      toast.success("Saved for offline — photos and linked pages aren't included");
+    } catch {
+      toast.error("Couldn't save this recipe for offline use");
+    } finally {
+      setBusy(false);
+    }
+  }
+
+  return (
+    <Button type="button" variant="outline" size="sm" disabled={busy} onClick={() => { void toggle(); }}>
+      {saved ? <Check className="h-3.5 w-3.5" /> : <Download className="h-3.5 w-3.5" />}
+      {saved ? "Saved offline" : "Save offline"}
+    </Button>
+  );
+}