fix(flutter): cacheFirst no longer hangs on no-match cold fetches

Liked tab loaded into an infinite spinner when the user had likes
in one category but not all three. Root cause: the three liked-tab
providers share one _populateLikeIds function. When the populate
writes track rows, drift watch fires for cached_likes (the table
all three providers watch). The track provider's stream re-emits
with rows.isNotEmpty → yields populated. The album and artist
streams re-emit with rows.isEmpty (user has no album/artist likes),
re-enter cacheFirst's rows-empty branch, fire populate AGAIN, drift
fires again, repeat — never yielding, .isLoading stays true forever,
UI spins.

Generalises beyond the liked case: any cacheFirst with a populate
that writes to a watched table but produces no rows matching this
filter would loop. Fix tracks coldFetchAttempted per subscription
so the first fetch is the only fetch via the rows-empty branch;
subsequent empty emissions yield empty. Also yields current rows
after a successful populate so a true no-op fetchAndPopulate (server
genuinely empty, fresh-install with no library data) doesn't hang
when drift doesn't re-emit for an empty batch.

For populated cases, the order is: spinner → brief empty yield from
the post-populate yield → drift watch re-emits with rows → populated.
UI flashes empty for one frame. Acceptable trade-off for the
no-spin guarantee.

Also matches the timeout pattern: liked providers' isOnline gains
the same 3-second timeout the home/library-list providers already
had, so a stuck connectivity check can't extend the hang.

flutter_client/lib/cache/cache_first.dart

@@ -48,9 +48,22 @@ Stream<T> cacheFirst<D, T>({
   // drift re-emission (otherwise the populate cycles forever).
   var revalidated = false;
 
+  // Tracks whether we've already tried a cold-cache fetch on this
+  // subscription. Without this, providers can spin forever in the
+  // rows-empty branch when fetchAndPopulate writes rows that don't
+  // match THIS filter — e.g. three liked-tab streams sharing one
+  // populate: the track populate writes track-typed rows, drift
+  // watch fires for the cached_likes table, the album stream
+  // re-emits with rows-empty (no album likes), the rows-empty
+  // branch re-fires populate, repeats forever. Setting this guard
+  // makes the first fetch attempt also the last for any given
+  // subscription.
+  var coldFetchAttempted = false;
+
   await for (final rows in driftStream) {
     if (rows.isNotEmpty) {
       yield toResult(rows);
+      coldFetchAttempted = true;
       // Stale-while-revalidate: yield cache immediately, then kick off
       // a REST refresh in the background. Drift watch() picks up the
       // resulting writes and re-emits via this same stream loop.
@@ -62,11 +75,25 @@ Stream<T> cacheFirst<D, T>({
       }
       continue;
     }
+    // rows is empty. If we've already attempted a cold fetch and
+    // drift is still empty for this filter, yield empty so the UI
+    // shows the no-content state instead of spinning forever.
+    if (coldFetchAttempted) {
+      yield toResult(rows);
+      continue;
+    }
+    coldFetchAttempted = true;
     if (await isOnline()) {
       try {
         await fetchAndPopulate();
-        // The drift watch() stream re-emits with the populated rows on
-        // the next loop iteration. Don't yield here.
+        // Yield the current (still-empty) rows so the UI moves past
+        // loading even if populate was a no-op for this filter
+        // (server returned nothing matching, or all rows were
+        // already in drift via sync). If populate DID write rows
+        // matching this filter, the drift watch's next emission
+        // yields them via the rows.isNotEmpty branch — UI briefly
+        // shows empty then populates, instead of spinning.
+        yield toResult(rows);
       } catch (e, st) {
         if (tag != null) {
           debugPrint('cacheFirst[$tag]: fetchAndPopulate failed: $e\n$st');

flutter_client/lib/library/library_screen.dart

@@ -242,7 +242,9 @@ final _likedTrackIdsProvider = StreamProvider<List<String>>((ref) {
     driftStream: query,
     fetchAndPopulate: () => _populateLikeIds(ref),
     toResult: _idsForEntity,
-    isOnline: () async => (await ref.read(connectivityProvider.future)),
+    isOnline: () async => (await ref
+        .read(connectivityProvider.future)
+        .timeout(const Duration(seconds: 3), onTimeout: () => true)),
     alwaysRefresh: true,
     tag: 'likedTrackIds',
   );
@@ -258,7 +260,9 @@ final _likedAlbumIdsProvider = StreamProvider<List<String>>((ref) {
     driftStream: query,
     fetchAndPopulate: () => _populateLikeIds(ref),
     toResult: _idsForEntity,
-    isOnline: () async => (await ref.read(connectivityProvider.future)),
+    isOnline: () async => (await ref
+        .read(connectivityProvider.future)
+        .timeout(const Duration(seconds: 3), onTimeout: () => true)),
     alwaysRefresh: true,
     tag: 'likedAlbumIds',
   );
@@ -274,7 +278,9 @@ final _likedArtistIdsProvider = StreamProvider<List<String>>((ref) {
     driftStream: query,
     fetchAndPopulate: () => _populateLikeIds(ref),
     toResult: _idsForEntity,
-    isOnline: () async => (await ref.read(connectivityProvider.future)),
+    isOnline: () async => (await ref
+        .read(connectivityProvider.future)
+        .timeout(const Duration(seconds: 3), onTimeout: () => true)),
     alwaysRefresh: true,
     tag: 'likedArtistIds',
   );