feat(agent): update import paths for gns3_copilot modules

Updated import statements across multiple agent files to use absolute paths starting with `gns3server.agent.gns3_copilot` instead of relative `gns3_copilot` imports. This ensures proper module resolution within the gns3-server package structure and prevents import errors when the agent is executed from different contexts.

gns3server/api/routes/controller/chat.py

@@ -21,7 +21,7 @@ API routes for GNS3 Copilot Chat integration.
 import json
 import logging
 import uuid
-from typing import Optional
+from typing import Optional, List
 
 from fastapi import APIRouter, Depends, HTTPException, Request, status
 from fastapi.responses import StreamingResponse