feat(#21): implement ollama integration

- Add Ollama client library (ollama npm package)
- Create LlmService for chat completion and embeddings
- Support streaming responses via Server-Sent Events
- Add configuration via env vars (OLLAMA_HOST, OLLAMA_TIMEOUT)
- Create endpoints: GET /llm/health, GET /llm/models, POST /llm/chat, POST /llm/embed
- Replace old OllamaModule with new LlmModule
- Add comprehensive tests with >85% coverage

Closes #21

apps/api/src/llm/index.ts

@@ -0,0 +1,4 @@
+export * from "./llm.module";
+export * from "./llm.service";
+export * from "./llm.controller";
+export * from "./dto";