fix: remove broken dev_tools router references after API route migration

The dev_tools API routes were moved to the monitoring module, but several
files still tried to import the non-existent admin_router. This caused
warnings during app startup.

Changes:
- Remove _get_admin_router() from definition.py
- Clear routes/__init__.py and routes/api/__init__.py of broken imports
- Update exceptions.py to import from monitoring.exceptions
- Update code_quality_service.py to import from monitoring.exceptions

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/modules/dev_tools/services/code_quality_service.py

@@ -12,7 +12,7 @@ from datetime import datetime, UTC
 from sqlalchemy import desc, func
 from sqlalchemy.orm import Session
 
-from app.exceptions import (
+from app.modules.monitoring.exceptions import (
     ScanParseException,
     ScanTimeoutException,
     ViolationNotFoundException,