✨(audio) assign users to diarization speaker results using VAD

Introduce a new user assignment mechanism to for more friendly output
than the current (SPEAKER_0, SPEAKER_1, ...). Use the VAD metadata to
compare speech intervals with those returned by WhisperX. User with the
highest overlap score above a defined threshold is assigned to each segment.
This method allows for multi-speaker scenarios for a single account.

src/agents/metadata_collector.py

@@ -177,7 +177,7 @@ class MetadataCollector:
 
     def save(self):
         """Serialize collected events and upload as JSON to S3."""
-        logger.info("Persisting metadata…")
+        logger.info("Persisting metadata...")
 
         participants = []
         for k, v in self.participants.items():
@@ -372,7 +372,7 @@ async def entrypoint(ctx: JobContext):
     await ctx.connect(auto_subscribe=AutoSubscribe.AUDIO_ONLY)
 
     async def cleanup():
-        logger.info("Shutting down metadata collector…")
+        logger.info("Shutting down metadata collector...")
         await metadata_collector.aclose()
 
     ctx.add_shutdown_callback(cleanup)