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>

tests/test_database_utils.py

@@ -0,0 +1,31 @@
+"""
+Tests for database utilities - AC4 (dual DB URL conversion)
+"""
+
+import pytest
+
+from database.utils import convert_to_async_url
+
+
+class TestConvertToAsyncUrl:
+    """AC4: PostgreSQL (prod) and SQLite (dev) URL conversion to async drivers."""
+
+    def test_postgresql_converted_to_asyncpg(self):
+        """postgresql:// -> postgresql+asyncpg://"""
+        url = "postgresql://user:pass@localhost:5432/db"
+        assert convert_to_async_url(url) == "postgresql+asyncpg://user:pass@localhost:5432/db"
+
+    def test_postgres_converted_to_asyncpg(self):
+        """postgres:// -> postgresql+asyncpg://"""
+        url = "postgres://user:pass@localhost:5432/db"
+        assert convert_to_async_url(url) == "postgresql+asyncpg://user:pass@localhost:5432/db"
+
+    def test_sqlite_converted_to_aiosqlite(self):
+        """sqlite:/// -> sqlite+aiosqlite:///"""
+        url = "sqlite:///./data/translate.db"
+        assert convert_to_async_url(url) == "sqlite+aiosqlite:///./data/translate.db"
+
+    def test_unknown_url_unchanged(self):
+        """Unknown scheme is returned unchanged."""
+        url = "mysql://localhost/db"
+        assert convert_to_async_url(url) == "mysql://localhost/db"