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/conftest.py

@@ -0,0 +1,40 @@
+"""
+Test configuration and fixtures
+"""
+
+from typing import AsyncGenerator
+
+import pytest_asyncio
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
+
+# In-memory SQLite: fully isolated, no disk state between test sessions
+TEST_DATABASE_URL = "sqlite+aiosqlite:///:memory:"
+
+
+@pytest_asyncio.fixture
+async def async_engine():
+    from database.models import Base
+
+    engine = create_async_engine(TEST_DATABASE_URL, echo=False)
+
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+
+    yield engine
+
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.drop_all)
+
+    await engine.dispose()
+
+
+@pytest_asyncio.fixture
+async def async_session(async_engine) -> AsyncGenerator[AsyncSession, None]:
+    async_session_factory = async_sessionmaker(
+        bind=async_engine,
+        class_=AsyncSession,
+        expire_on_commit=False,
+    )
+
+    async with async_session_factory() as session:
+        yield session