feat: production deployment - full update with providers, admin, glossaries, pricing, tests

Major changes across backend, frontend, infrastructure:
- Provider system with model selection (Google, DeepL, OpenAI, Ollama, Google Cloud)
- Admin panel: user management, pricing, settings
- Glossary system with CSV import/export
- Subscription and tier quota management
- Security hardening (rate limiting, API key auth, path traversal fixes)
- Docker compose for dev, prod, and IONOS deployment
- Alembic migrations for new tables
- Frontend: dashboard, pricing page, landing page, i18n (en/fr)
- Test suite and verification scripts

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

middleware/error_handler.py

@@ -13,12 +13,9 @@ from starlette.exceptions import HTTPException as StarletteHTTPException
 # Import APIKeyError for handling
 from middleware.api_key_auth import APIKeyError
 
-try:
-    import structlog
+from core.logging import get_logger
 
-    logger = structlog.get_logger(__name__)
-except ImportError:
-    logger = logging.getLogger(__name__)
+logger = get_logger(__name__)
 
 
 def format_error_response(