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>

data/pricing_overrides.json

@@ -0,0 +1,20 @@
+{
+  "starter": {
+    "price_monthly": 7.0,
+    "price_yearly": 67.2,
+    "stripe_price_id_monthly": "",
+    "stripe_price_id_yearly": ""
+  },
+  "pro": {
+    "price_monthly": 19.0,
+    "price_yearly": 182.4,
+    "stripe_price_id_monthly": "",
+    "stripe_price_id_yearly": ""
+  },
+  "business": {
+    "price_monthly": 49.0,
+    "price_yearly": 470.4,
+    "stripe_price_id_monthly": "",
+    "stripe_price_id_yearly": ""
+  }
+}