[TASK] LLM Model (LangChain / n8n)

**Description:**  
Choose and integrate an LLM model to handle user queries.

**Scope:**
- Evaluate available models (e.g., OpenAI, local models)
- Integrate via LangChain or n8n
- Design prompts
- Test response quality

**Acceptance Criteria:**
- [ ] Model responds to user queries
- [ ] Integration works within the pipeline
