feat(M3-004,M3-006): add OpenRouter adapter and Ollama embedding support

- M3-004: Implement OpenRouterAdapter using openai SDK with custom base URL
  (https://openrouter.ai/api/v1). Fetches model catalog on registration,
  gracefully degrades when OPENROUTER_API_KEY is absent, streams completions
  via OpenAI-compatible API.

- M3-006: Enhance OllamaAdapter with embedding model registration
  (nomic-embed-text, mxbai-embed-large) and an embed(text, model?) method
  that calls Ollama's /api/embeddings endpoint. listModels() now returns
  both completion and embedding models. Prepares for M3-009 EmbeddingService.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/gateway/package.json

@@ -46,6 +46,7 @@
     "dotenv": "^17.3.1",
     "fastify": "^5.0.0",
     "node-cron": "^4.2.1",
+    "openai": "^6.32.0",
     "reflect-metadata": "^0.2.0",
     "rxjs": "^7.8.0",
     "socket.io": "^4.8.0",