Add audio generation config, refactor rep_announcer

- AudioConfig now includes rep_max_count and rep_audio_dir
- app/audio/generate.py uses config instead of hardcoded constants
- RepAnnouncer rewrote with pre-generated audio cache
- Supports Windows winsound, macOS afplay, Linux paplay/aplay
- Pin requirements back to mediapipe==0.10.21 with numpy<2

configs/models.py

@@ -46,6 +46,15 @@ class AudioConfig:
     rep_announcer_enabled: bool = True
     rep_announcer_rate: int = 185
     rep_announcer_volume: float = 1.0
+    rep_max_count: int = 200
+    rep_audio_dir: str = ""
+
+    @property
+    def resolved_audio_dir(self) -> Path:
+        """返回语音文件目录的绝对路径"""
+        if self.rep_audio_dir:
+            return Path(self.rep_audio_dir)
+        return Path(__file__).resolve().parent.parent / "app" / "audio" / "reps"
 
 
 @dataclass