✨ | Add MPRIS integration for media key control

Implements org.mpris.MediaPlayer2 and org.mpris.MediaPlayer2.Player
D-Bus interfaces, allowing desktop environment media keys and tools
like playerctl to control playback (play, pause, next, previous)
and display now-playing metadata.

Also adds _FallbackServiceInterface, _FallbackVariant and
_FallbackNameFlag so all tests pass without dbus-fast installed;
the module gracefully degrades when the library is unavailable.

gui.py

@@ -80,6 +80,7 @@ except (ImportError, OSError):
 
 from config import SETTINGS, get_setting, save_setting, save_volume
 from discord_rpc import DiscordRPC
+from mpris import MprisManager
 from music_db import MusicDB
 from player import AudioPlayer, SearchWorker, _best_thumbnail
 
@@ -2279,6 +2280,9 @@ class TunettiWindow(QMainWindow):
         self.db = MusicDB(SETTINGS["db_path"])
         self.rpc = DiscordRPC(SETTINGS["discord_client_id"])
         self.player = AudioPlayer(self)
+        self.mpris = MprisManager()
+        self.mpris.start()
+        self._connect_mpris()
 
         # ── Central widget ──
         central = QWidget()
@@ -2947,6 +2951,54 @@ class TunettiWindow(QMainWindow):
         except Exception as exc:
             log.error("_poll_minimized error: %s", exc)
 
+    # ── MPRIS integration ──
+
+    def _connect_mpris(self) -> None:
+        """Wire MPRIS bridge signals to the player."""
+        bridge = self.mpris.get_bridge()
+        if bridge is None:
+            return
+
+        # MPRIS → player (cross-thread via Qt queued connections)
+        bridge.play_requested.connect(self.player.resume)
+        bridge.pause_requested.connect(self.player.pause)
+        bridge.play_pause_requested.connect(self.player.toggle_pause)
+        bridge.stop_requested.connect(self.player.stop_playback)
+        bridge.next_requested.connect(self.player.skip)
+        bridge.previous_requested.connect(self.player.previous)
+
+        # Player → MPRIS state updates
+        self.player.playback_state_changed.connect(
+            self._on_mpris_state_changed
+        )
+        self.player.song_started.connect(self._on_mpris_song_started)
+        self.player.song_ended.connect(self._on_mpris_song_ended)
+
+    def _on_mpris_state_changed(self, state: str) -> None:
+        """Forward playback state changes to MPRIS."""
+        song = self.player.get_current()
+        self.mpris.notify_state_changed(
+            state, song, self.player.has_previous()
+        )
+
+    def _on_mpris_song_started(self, song: dict) -> None:
+        """Forward new song metadata to MPRIS."""
+        self.mpris.notify_state_changed(
+            "playing", song, self.player.has_previous()
+        )
+
+    def _on_mpris_song_ended(self, video_id: str) -> None:
+        """Forward song end to MPRIS."""
+        song = self.player.get_current()
+        if song:
+            self.mpris.notify_state_changed(
+                "playing", song, self.player.has_previous()
+            )
+        else:
+            self.mpris.notify_state_changed(
+                "stopped", None, False
+            )
+
     # ── Public accessors (for child dialogs) ──
 
     def get_visualizer(self) -> AudioVisualizer:
@@ -2982,6 +3034,7 @@ class TunettiWindow(QMainWindow):
     def closeEvent(self, event) -> None:
         # Flush any pending volume save before closing
         self._playback.flush_volume()
+        self.mpris.stop()
         self.player.shutdown()
         self.rpc.stop()
         self.db.close()