fix(flutter): album/artist detail covers + cacheFirst tracing for hangs

Album detail screen rendered the cover slot as a bare slate Container
— no actual image. Wire ServerImage at /api/albums/<id>/cover (96dp,
rounded). Same for artist detail: ClipOval around ServerImage of the
artist's coverUrl, falling back to slate when empty.

Artist navigation hang: artistProvider goes through cacheFirst, which
had no logging — so we couldn't see whether the cold-cache fetch was
running. Add an optional `tag` parameter that, when set, debugPrints
each step (drift hit/miss, connectivity, fetch start/done/error).
Wire tags into artistProvider and artistAlbumsProvider, plus add the
3s connectivity timeout there too as belt-and-suspenders.

Next test pass should show cacheFirst[artist(<id>)]: lines that
pinpoint where the artist screen is sticking.

flutter_client/lib/library/album_detail_screen.dart

@@ -6,6 +6,7 @@ import '../cache/audio_cache_manager.dart';
 import '../cache/db.dart';
 import '../likes/like_button.dart';
 import '../player/player_provider.dart';
+import '../shared/widgets/server_image.dart';
 import '../theme/theme_extension.dart';
 import 'library_providers.dart';
 import 'widgets/track_row.dart';
@@ -27,7 +28,18 @@ class AlbumDetailScreen extends ConsumerWidget {
               Padding(
                 padding: const EdgeInsets.all(16),
                 child: Row(children: [
-                  Container(width: 96, height: 96, color: fs.slate),
+                  ClipRRect(
+                    borderRadius: BorderRadius.circular(6),
+                    child: SizedBox(
+                      width: 96,
+                      height: 96,
+                      child: ServerImage(
+                        url: '/api/albums/$id/cover',
+                        fit: BoxFit.cover,
+                        fallback: Container(color: fs.slate),
+                      ),
+                    ),
+                  ),
                   const SizedBox(width: 16),
                   Expanded(child: Column(
                     crossAxisAlignment: CrossAxisAlignment.start,

flutter_client/lib/library/artist_detail_screen.dart

@@ -6,6 +6,7 @@ import '../api/endpoints/likes.dart';
 import '../likes/like_button.dart';
 import '../models/album.dart';
 import '../player/player_provider.dart';
+import '../shared/widgets/server_image.dart';
 import '../theme/theme_extension.dart';
 import 'library_providers.dart';
 import 'widgets/album_card.dart';
@@ -30,9 +31,18 @@ class ArtistDetailScreen extends ConsumerWidget {
           Padding(
             padding: const EdgeInsets.all(16),
             child: Row(children: [
-              Container(
-                width: 96, height: 96,
-                decoration: BoxDecoration(color: fs.slate, shape: BoxShape.circle),
+              ClipOval(
+                child: SizedBox(
+                  width: 96,
+                  height: 96,
+                  child: a.coverUrl.isEmpty
+                      ? Container(color: fs.slate)
+                      : ServerImage(
+                          url: a.coverUrl,
+                          fit: BoxFit.cover,
+                          fallback: Container(color: fs.slate),
+                        ),
+                ),
               ),
               const SizedBox(width: 16),
               Expanded(

flutter_client/lib/library/library_providers.dart

@@ -61,8 +61,10 @@ final artistProvider =
     toResult: (rows) => rows.isEmpty
         ? const ArtistRef(id: '', name: '')
         : rows.first.toRef(),
-    isOnline: () async =>
-        (await ref.read(connectivityProvider.future)),
+    isOnline: () async => (await ref
+        .read(connectivityProvider.future)
+        .timeout(const Duration(seconds: 3), onTimeout: () => true)),
+    tag: 'artist($id)',
   );
 });
 
@@ -90,8 +92,10 @@ final artistAlbumsProvider =
       final artist = r.readTableOrNull(db.cachedArtists);
       return album.toRef(artistName: artist?.name ?? '');
     }).toList(),
-    isOnline: () async =>
-        (await ref.read(connectivityProvider.future)),
+    isOnline: () async => (await ref
+        .read(connectivityProvider.future)
+        .timeout(const Duration(seconds: 3), onTimeout: () => true)),
+    tag: 'artistAlbums($artistId)',
   );
 });