chore(V2): cleanup quality gate

- ruff: contextlib.suppress al posto di try/except/pass (client_registry, test_env_routing)
- rimozione services/ legacy (residuo da git rm)
- fix integration test fixture: rimosso sys.modules.pop che inquinava module references nei test successivi (test_audit, test_client_init_default_http)

254 test passano. Ruff: clean. Mypy: 68 warning preesistenti dal codice V1 migrato (strict=false).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/unit/test_auth.py

@@ -1,4 +1,3 @@
-import pytest
 from fastapi import FastAPI, Request
 from fastapi.testclient import TestClient
 
@@ -92,6 +91,7 @@ def test_mainnet_token_sets_env_mainnet():
 def test_uses_compare_digest():
     """Verifica che _check_token usi secrets.compare_digest (timing-safe)."""
     import inspect
+
     from cerbero_mcp import auth
 
     src = inspect.getsource(auth)