feat: complete analytics module self-containment

Migrate analytics module to fully self-contained structure:

- routes/api/vendor.py - API endpoints
- routes/pages/vendor.py - Page routes with full implementation
- services/stats_service.py - Business logic (moved from app/services)
- services/usage_service.py - Usage tracking (moved from app/services)
- schemas/stats.py - Pydantic schemas (moved from models/schema)
- models/__init__.py - Model exports
- templates/analytics/vendor/ - Templates (moved from app/templates)
- static/vendor/js/ - JavaScript (moved from static/vendor)
- locales/ - Translations (en, de, fr, lu)
- exceptions.py - Module exceptions

Removed legacy files:
- app/modules/analytics/routes/vendor.py (replaced by routes/pages/)
- static/admin/js/analytics.js (unused)

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

static/admin/js/analytics.js

@@ -1 +0,0 @@
-// Admin analytics