Unify web player controls and add volume control

frontend/lib/pages/player_page.dart

@@ -42,6 +42,7 @@ class _PlayerPageState extends State<PlayerPage> {
   bool _isRefreshing = false;
   bool _isFullscreen = false;
   bool _controlsVisible = true;
+  double _volume = kIsWeb ? 0.0 : 1.0;
   int _playerVersion = 0;
   String _selectedResolution = 'Source';
   List<String> _availableResolutions = const ['Source'];
@@ -63,6 +64,7 @@ class _PlayerPageState extends State<PlayerPage> {
     _controller = VideoPlayerController.networkUrl(Uri.parse(playbackUrl));
     try {
       await _controller!.initialize();
+      await _controller!.setVolume(_volume);
       _controller!.play();
       if (mounted) setState(() {});
     } catch (e) {
@@ -254,6 +256,76 @@ class _PlayerPageState extends State<PlayerPage> {
     _showControls();
   }
 
+  Future<void> _setVolume(double volume) async {
+    final nextVolume = volume.clamp(0.0, 1.0);
+    if (!mounted) {
+      return;
+    }
+
+    setState(() => _volume = nextVolume);
+
+    if (!kIsWeb && _controller != null) {
+      await _controller!.setVolume(nextVolume);
+    }
+  }
+
+  Future<void> _openVolumeSheet() async {
+    _showControls();
+    await showModalBottomSheet<void>(
+      context: context,
+      builder: (context) {
+        return SafeArea(
+          child: Padding(
+            padding: const EdgeInsets.fromLTRB(20, 16, 20, 28),
+            child: StatefulBuilder(
+              builder: (context, setSheetState) {
+                return Column(
+                  mainAxisSize: MainAxisSize.min,
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: [
+                    Text(
+                      'Volume',
+                      style: Theme.of(context).textTheme.titleMedium,
+                    ),
+                    const SizedBox(height: 12),
+                    Row(
+                      children: [
+                        Icon(
+                          _volume == 0
+                              ? Icons.volume_off
+                              : _volume < 0.5
+                              ? Icons.volume_down
+                              : Icons.volume_up,
+                        ),
+                        Expanded(
+                          child: Slider(
+                            value: _volume,
+                            min: 0,
+                            max: 1,
+                            divisions: 20,
+                            label: '${(_volume * 100).round()}%',
+                            onChanged: (value) {
+                              setSheetState(() => _volume = value);
+                              _setVolume(value);
+                            },
+                          ),
+                        ),
+                        SizedBox(
+                          width: 48,
+                          child: Text('${(_volume * 100).round()}%'),
+                        ),
+                      ],
+                    ),
+                  ],
+                );
+              },
+            ),
+          ),
+        );
+      },
+    );
+  }
+
   void _showControls() {
     _controlsHideTimer?.cancel();
     if (mounted) {
@@ -439,6 +511,7 @@ class _PlayerPageState extends State<PlayerPage> {
                   ? WebStreamPlayer(
                       key: ValueKey('web-player-$_playerVersion'),
                       streamUrl: _currentPlaybackUrl(),
+                      volume: _volume,
                     )
                   : _controller != null && _controller!.value.isInitialized
                   ? AspectRatio(
@@ -550,6 +623,15 @@ class _PlayerPageState extends State<PlayerPage> {
                     label: "Refresh",
                     onPressed: _refreshPlayer,
                   ),
+                  _buildControlButton(
+                    icon: _volume == 0
+                        ? Icons.volume_off
+                        : _volume < 0.5
+                        ? Icons.volume_down
+                        : Icons.volume_up,
+                    label: "Volume",
+                    onPressed: _openVolumeSheet,
+                  ),
                   _buildControlButton(
                     icon: _showDanmaku ? Icons.subtitles : Icons.subtitles_off,
                     label: _showDanmaku ? "Danmaku On" : "Danmaku Off",