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>

.gitignore

@@ -40,7 +40,15 @@ outputs/
 temp/
 translated_files/
 translated_test.*
-data/
+
+# Runtime data (users, provider config, glossaries) — managed at runtime, not in git
+data/users.json
+data/*.db
+data/*.sqlite
+
+# Keep these in git (templates/defaults only)
+# data/provider_settings.json → commiter uniquement si pas de clés dedans
+# data/pricing_overrides.json → OK à commiter
 
 # Logs
 *.log
@@ -50,6 +58,13 @@ logs/
 .venv/
 uv.lock
 
-# Test files
-test_*.py
-test_*.ipynb
+# Test files (only at repo root; keep tests/ folder tracked)
+/test_*.py
+/test_*.ipynb
+
+# macOS
+.DS_Store
+
+# Screenshots and debug files at root
+*.png
+*.jpg