🎤 Feature B: Artist-Browse UI (Phase 2, Part 3/3)

- Toggle-Buttons in Navidrome-Tab: "📀 Alben" ↔ "🎤 Künstler"
- Artist-Liste zeigt Namen pro Künstler, Tap lädt alle Songs des Künstlers
- _playArtist() Methode lädt Künstler-Songs via getArtistSongs() API
- Albums/Artists sind Lazy-Loaded (nur beim Toggle laden)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XJzQjUtnvYUtHdnTs3iCru

lib/library/library_screen.dart

@@ -253,7 +253,9 @@ class _NavidromeTab extends StatefulWidget {
 class _NavidromeTabState extends State<_NavidromeTab> {
   late final NavidromeService _nav = NavidromeService();
   List<SubsonicAlbum> _albums = [];
+  List<SubsonicArtist> _artists = [];
   bool _loading = false;
+  bool _showArtists = false;
 
   @override
   void initState() {
@@ -286,6 +288,23 @@ class _NavidromeTabState extends State<_NavidromeTab> {
     }
   }
 
+  Future<void> _loadArtists() async {
+    if (!_nav.istVerbunden) return;
+    setState(() => _loading = true);
+    try {
+      final artists = await _nav.getArtists();
+      if (mounted) {
+        setState(() {
+          _artists = artists;
+          _loading = false;
+        });
+      }
+    } catch (e) {
+      if (mounted) setState(() => _loading = false);
+      debugPrint('Fehler beim Laden der Künstler: $e');
+    }
+  }
+
   @override
   Widget build(BuildContext context) {
     if (!_nav.istVerbunden) {
@@ -331,25 +350,79 @@ class _NavidromeTabState extends State<_NavidromeTab> {
       );
     }
 
-    return ListView.builder(
-      padding: const EdgeInsets.all(12),
-      itemCount: _albums.length,
-      itemBuilder: (context, i) {
-        final album = _albums[i];
-        return Card(
-          margin: const EdgeInsets.only(bottom: 8),
-          child: ListTile(
-            leading: Icon(
-              Icons.album,
-              size: 48,
-              color: Colors.redAccent.withValues(alpha: 0.5),
-            ),
-            title: Text(album.name),
-            subtitle: Text('${album.songCount} Songs'),
-            onTap: () => _playAlbum(album),
+    return Column(
+      children: [
+        Padding(
+          padding: const EdgeInsets.all(12),
+          child: Row(
+            children: [
+              Expanded(
+                child: FilledButton(
+                  onPressed: () => setState(() {
+                    _showArtists = false;
+                    if (_albums.isEmpty) _loadAlbums();
+                  }),
+                  style: FilledButton.styleFrom(
+                    backgroundColor: !_showArtists ? Colors.redAccent : Colors.grey.shade700,
+                  ),
+                  child: const Text('📀 Alben'),
+                ),
+              ),
+              const SizedBox(width: 8),
+              Expanded(
+                child: FilledButton(
+                  onPressed: () => setState(() {
+                    _showArtists = true;
+                    if (_artists.isEmpty) _loadArtists();
+                  }),
+                  style: FilledButton.styleFrom(
+                    backgroundColor: _showArtists ? Colors.redAccent : Colors.grey.shade700,
+                  ),
+                  child: const Text('🎤 Künstler'),
+                ),
+              ),
+            ],
           ),
-        );
-      },
+        ),
+        Expanded(
+          child: _showArtists
+              ? ListView.builder(
+                  padding: const EdgeInsets.symmetric(horizontal: 12),
+                  itemCount: _artists.length,
+                  itemBuilder: (context, i) {
+                    final artist = _artists[i];
+                    return Card(
+                      margin: const EdgeInsets.only(bottom: 8),
+                      child: ListTile(
+                        leading: const Icon(Icons.person, size: 48),
+                        title: Text(artist.name),
+                        onTap: () => _playArtist(artist),
+                      ),
+                    );
+                  },
+                )
+              : ListView.builder(
+                  padding: const EdgeInsets.symmetric(horizontal: 12),
+                  itemCount: _albums.length,
+                  itemBuilder: (context, i) {
+                    final album = _albums[i];
+                    return Card(
+                      margin: const EdgeInsets.only(bottom: 8),
+                      child: ListTile(
+                        leading: Icon(
+                          Icons.album,
+                          size: 48,
+                          color: Colors.redAccent.withValues(alpha: 0.5),
+                        ),
+                        title: Text(album.name),
+                        subtitle: Text('${album.songCount} Songs'),
+                        onTap: () => _playAlbum(album),
+                      ),
+                    );
+                  },
+                ),
+        ),
+      ],
     );
   }
 
@@ -387,4 +460,33 @@ class _NavidromeTabState extends State<_NavidromeTab> {
       );
     }
   }
+
+  Future<void> _playArtist(SubsonicArtist artist) async {
+    final handler = context.read<MeloAudioHandler>();
+    try {
+      final songs = await _nav.getArtistSongs(artist.id);
+      if (songs.isEmpty) {
+        if (!mounted) return;
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(content: Text('Künstler hat keine Songs')),
+        );
+        return;
+      }
+      final items = songs
+          .map((s) => MediaItem(
+            id: _nav.streamUrl(s.id).toString(),
+            title: s.titel,
+            artist: s.kuenstler,
+            album: s.album,
+            duration: Duration(seconds: s.dauerSekunden),
+          ))
+          .toList();
+      await handler.loadPlaylist(items);
+    } catch (e) {
+      if (!mounted) return;
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text('Fehler: $e')),
+      );
+    }
+  }
 }