feat(copilot): refactor JWT token handling and improve metadata tracking

- Move JWT token from state to configurable context for better security and request isolation
- Add user_id parameter to agent service for enhanced metadata tracking
- Update checkpoint directory name from .gns3-copilot to gns3-copilot
- Implement context-aware JWT token management using ContextVar
- Improve tool node to extract JWT token from config instead of state

gns3server/api/routes/controller/chat.py

@@ -117,6 +117,7 @@ async def stream_chat(
                 message=request.message,
                 session_id=session_id,
                 project_id=str(project.id),
+                user_id=user_id,
                 jwt_token=jwt_token,
                 mode=request.mode,
                 llm_config=llm_config