Fix mpv pause state when loading new media

Fixes #107

This fixes an issue where loading a new media URL while the player
was paused would keep playback paused, causing Music Assistant to
show the player as playing while no audio was audible.

The mpv pause state is now always set explicitly when starting playback,
ensuring deterministic behavior

linux_voice_assistant/player/base.py

@@ -0,0 +1,25 @@
+from abc import ABC, abstractmethod
+from .state import PlayerState
+
+
+class AudioPlayer(ABC):
+
+    @abstractmethod
+    def play(self, url: str) -> None:
+        pass
+
+    @abstractmethod
+    def pause(self) -> None:
+        pass
+
+    @abstractmethod
+    def resume(self) -> None:
+        pass
+
+    @abstractmethod
+    def stop(self) -> None:
+        pass
+
+    @abstractmethod
+    def state(self) -> PlayerState:
+        pass