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>

.env.production

@@ -58,7 +58,18 @@ RATE_LIMIT_TRANSLATIONS_PER_DAY=500
 # Security (CHANGE THESE!)
 # ===========================================
 ADMIN_USERNAME=admin
-ADMIN_PASSWORD=CHANGE_THIS_SECURE_PASSWORD
+
+# Use bcrypt hash — NEVER store plaintext password in production
+# Generate with: python -c "from passlib.context import CryptContext; print(CryptContext(schemes=['bcrypt']).hash('YOUR_PASSWORD'))"
+ADMIN_PASSWORD_HASH=
+
+# JWT secret key — REQUIRED, generates random key at startup if not set (breaks auth on restart)
+# Generate with: python -c "import secrets; print(secrets.token_urlsafe(64))"
+JWT_SECRET_KEY=
+
+# Admin token secret — REQUIRED, generates random key at startup if not set (breaks admin sessions on restart)
+# Generate with: python -c "import secrets; print(secrets.token_hex(32))"
+ADMIN_TOKEN_SECRET=
 
 # CORS Configuration
 CORS_ORIGINS=https://translate.yourdomain.com