feat: Add OpenRouter provider integration with 100+ AI models

[vinodkrishna221]

• Implement OpenRouter API client using OpenAI SDK wrapper
• Create model service with 24-hour caching and advanced filtering
• Add REST API endpoint (/api/models) for model discovery
• Create ModelSelector React component with search and filters
• Integrate OpenRouter into code generation and intent analysis
• Add 6 example OpenRouter models to configuration
• Support filtering by: free/paid, type, context length, provider
• Include comprehensive documentation and testing guides
• Maintain backward compatibility with existing providers
• Add error handling and security best practices

Files Created:

• lib/ai/openrouter-client.ts - API client wrapper
• lib/ai/model-service.ts - Model management service
• app/api/models/route.ts - REST API endpoint
• components/app/ModelSelector.tsx - UI component
• docs/OPENROUTER_INTEGRATION.md - Technical guide
• docs/OPENROUTER_SETUP.md - Setup guide
• docs/OPENROUTER_TESTING.md - Testing guide
• docs/OPENROUTER_COMPLETE.md - Overview
• docs/RESOURCE_GUIDE.md - Documentation index
• docs/IMPLEMENTATION_SUMMARY.txt - Visual summary

Files Modified:

• config/app.config.ts - Added OpenRouter models
• app/api/generate-ai-code-stream/route.ts - OpenRouter support
• app/api/analyze-edit-intent/route.ts - OpenRouter support
• README.md - OpenRouter setup instructions

Features:
✓ Access 100+ AI models (many free)
✓ Advanced model filtering
✓ Real-time search
✓ 24-hour caching for performance
✓ Production-ready code
✓ Full TypeScript support
✓ Comprehensive documentation