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/routes/pages/__init__.py

@@ -1,4 +1,2 @@
-# Page routes will be added here
-# TODO: Add HTML page routes for admin/vendor dashboards
-
-__all__ = []
+# app/modules/dev_tools/routes/pages/__init__.py
+"""Dev tools module page routes."""