fix: session stability improvements

- Fix docker client initialization bug in app.py (context manager was closing client)
- Add restart_session() method to preserve session IDs during container restarts
- Add 60-second startup grace period before health checking new sessions
- Fix _stop_container and _get_container_info to use docker_service API consistently
- Disable mDNS in Dockerfile to prevent Bonjour service name conflicts
- Remove old container before restart to free port bindings

session-manager/app.py

@@ -5,7 +5,6 @@ from fastapi import FastAPI
 
 from config import USE_ASYNC_DOCKER, USE_DATABASE_STORAGE
 from session_manager import session_manager
-from async_docker_client import get_async_docker_client
 from http_pool import init_http_pool, shutdown_http_pool
 from database import init_database, shutdown_database, run_migrations
 from container_health import (
@@ -43,12 +42,9 @@ async def lifespan(app: FastAPI):
                 session_manager._load_sessions_from_file()
 
     try:
-        docker_client = None
-        if USE_ASYNC_DOCKER:
-            async with get_async_docker_client() as client:
-                docker_client = client._docker if hasattr(client, "_docker") else None
-        else:
-            docker_client = session_manager.docker_service
+        # Use the session manager's docker_service for health monitoring
+        # This ensures the docker client stays alive for the lifetime of the application
+        docker_client = session_manager.docker_service
 
         await start_container_health_monitoring(session_manager, docker_client)
         logger.info("Container health monitoring started")