feat: hide tunnel UI for terminal sessions and show session metadata

Backend:
- Add created_at to get_user_sessions response

Frontend:
- Hide tunnel error badges, probe output, and 'Recreate Tunnel' button for terminal-only sessions
- Show session start time (created_at) in active sessions list
- Show repository configuration (clone_mode, branch) for each session
- Skip health check polling for terminal-only sessions
- Update Session type to include created_at field

apps/api/src/api/tool_instances.py

@@ -1437,6 +1437,7 @@ async def get_user_sessions(
             "url": instance.url,
             "clone_mode": instance.clone_mode,
             "branch": instance.branch,
+            "created_at": instance.created_at.isoformat() if instance.created_at else None,
         })
 
     return {"sessions": sessions}