feat(onboarding): auto-import subscriptions after read grant + empty-feed guidance

After read access is granted the wizard now imports the user's YouTube
subscriptions automatically (with a "Building your feed…" progress state), so a
new user lands on a populated feed — channels already in the shared catalog show
up instantly, new ones backfill in the background. The empty feed now prompts
users without read access to set up via the wizard instead of a bare message.

frontend/src/components/Feed.tsx

@@ -26,10 +26,14 @@ export default function Feed({
   filters,
   setFilters,
   view,
+  canRead,
+  onOpenWizard,
 }: {
   filters: FeedFilters;
   setFilters: (f: FeedFilters) => void;
   view: "grid" | "list";
+  canRead: boolean;
+  onOpenWizard: () => void;
 }) {
   const [overrides, setOverrides] = useState<Record<string, string>>({});
   const [activeVideo, setActiveVideo] = useState<Video | null>(null);
@@ -125,8 +129,26 @@ export default function Feed({
 
   if (query.isLoading) return <div className="p-8 text-muted">Loading feed…</div>;
   if (query.isError) return <div className="p-8 text-muted">Couldn't load the feed.</div>;
-  if (items.length === 0)
+  if (items.length === 0) {
+    if (!canRead)
+      return (
+        <div className="p-8 grid place-items-center text-center">
+          <div className="max-w-sm">
+            <h2 className="text-lg font-semibold">Your feed is empty</h2>
+            <p className="text-sm text-muted mt-2 mb-4">
+              Connect your YouTube account to import your subscriptions and build your feed.
+            </p>
+            <button
+              onClick={onOpenWizard}
+              className="inline-flex items-center justify-center gap-2 px-5 py-2.5 rounded-xl font-semibold bg-accent text-accent-fg hover:opacity-90 transition"
+            >
+              Set up my feed
+            </button>
+          </div>
+        </div>
+      );
     return <div className="p-8 text-muted">No videos match these filters.</div>;
+  }
 
   return (
     <div className="p-4">