refactor(api): migrate server to fastapi and uvicorn

Replace the Microdot-only entrypoint with a CombinedASGI app that
handles FastAPI routes (audio API, websocket, dev live-reload) while
delegating the rest to Microdot. Suppress noisy /__dev/ access logs
during live-reload polling.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/start.sh

@@ -35,4 +35,4 @@ if [ -z "$PYTHON" ]; then
 fi
 
 cd "$ROOT/src"
-exec "$PYTHON" -u main.py
+exec "$PYTHON" -u -m uvicorn fastapi_app:app --host 0.0.0.0 --port "$PORT"