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/provider_settings.json

@@ -0,0 +1,61 @@
+{
+  "google": {
+    "enabled": true,
+    "api_key": null,
+    "base_url": null,
+    "model": null,
+    "timeout": 30,
+    "max_retries": 3
+  },
+  "deepl": {
+    "enabled": false,
+    "api_key": null,
+    "base_url": null,
+    "model": null,
+    "timeout": 30,
+    "max_retries": 3
+  },
+  "openai": {
+    "enabled": false,
+    "api_key": null,
+    "base_url": null,
+    "model": "gpt-4o-mini",
+    "timeout": 30,
+    "max_retries": 3
+  },
+  "ollama": {
+    "enabled": false,
+    "api_key": null,
+    "base_url": "http://localhost:11434",
+    "model": "gpt-oss:20b",
+    "timeout": 30,
+    "max_retries": 3
+  },
+  "openrouter": {
+    "enabled": true,
+    "api_key": null,
+    "base_url": null,
+    "model": "deepseek/deepseek-v3.2",
+    "timeout": 30,
+    "max_retries": 3
+  },
+  "openrouter_premium": {
+    "enabled": false,
+    "api_key": null,
+    "base_url": null,
+    "model": "anthropic/claude-3.5-haiku",
+    "timeout": 30,
+    "max_retries": 3
+  },
+  "zai": {
+    "enabled": false,
+    "api_key": null,
+    "base_url": "https://api.x.ai/v1",
+    "model": "grok-2-1212",
+    "timeout": 30,
+    "max_retries": 3
+  },
+  "fallback_chain": "google,deepl,openai,ollama,openrouter,zai",
+  "fallback_chain_classic": "google,deepl",
+  "fallback_chain_llm": "ollama,openai,openrouter,zai"
+}