Media controls (MPRIS, Windows SMTC); stop old tracks when switching

Settings.py

@@ -137,6 +137,8 @@ def ShowSettingsDialog(TheApp: App, OnSaved: Callable[[bool], None], OnClearCach
     SeekField = _NumberField("Arrow keys seek by (seconds, Audio mode)", Config.SeekSeconds)
     AdvanceSwitch = ft.Switch(label="Audio mode plays the next file in the folder when one ends",
                               value=Config.AudioAutoAdvance)
+    MediaSwitch = ft.Switch(label="Show in the system's media controls and answer media keys",
+                            value=Config.MediaControls)
 
     # Music: one folder per line, plus a Browse button that adds a line.
     FoldersField = ft.TextField(label="Music folders (one per line)", value="\n".join(Config.MusicFolders),
@@ -212,6 +214,9 @@ def ShowSettingsDialog(TheApp: App, OnSaved: Callable[[bool], None], OnClearCach
                 _Note("Opening files with SaraTune (e.g. from a file manager) always starts in Audio mode."),
                 SeekField,
                 AdvanceSwitch,
+                MediaSwitch,
+                _Note("Media controls: the desktop's media widget and lock screen (MPRIS on Linux), the media "
+                      "overlay on Windows. Changing it applies the next time SaraTune starts."),
                 ft.Divider(height=1, color=Palette.Surface1),
                 OwnAppearance,
             ],
@@ -271,6 +276,7 @@ def ShowSettingsDialog(TheApp: App, OnSaved: Callable[[bool], None], OnClearCach
         Config.StartMode = StartMode.value or Config.StartMode
         Config.SeekSeconds = _ReadInt(SeekField, Config.SeekSeconds, 1)
         Config.AudioAutoAdvance = AdvanceSwitch.value
+        Config.MediaControls = MediaSwitch.value
         Config.MusicFolders = [os.path.expanduser(Line.strip()) for Line in (FoldersField.value or "").splitlines()
                                if Line.strip()]
         Config.ScanOnStart = ScanSwitch.value