chore: remove unused uuid import in app.py

app.py imports uuid but never uses it (pyflakes: 'uuid imported but
unused'). Drop the dead import — no behaviour change.

app.py

@@ -34,7 +34,6 @@ from dotenv import load_dotenv
 # is silently ignored and the user is unexpectedly forced to log in (issue #142).
 # utf-8-sig reads plain UTF-8 (no BOM) identically, so this is safe everywhere.
 load_dotenv(encoding="utf-8-sig")
-import uuid
 
 import asyncio
 import logging