Integrate OpenAI for natural language step creation

**Description:**
Use AI to convert natural language descriptions into automation steps.

**Tasks:**
- [ ] Integrate OpenAI API
- [ ] Design prompt templates
- [ ] Parse AI responses
- [ ] Validate generated steps
- [ ] Add refinement UI
- [ ] Handle API errors
- [ ] Test accuracy

**Acceptance Criteria:**
- Natural language converted
- Steps validated
- Refinement possible
- Accuracy >70%