New features:
- Review Code button sends generated code back to AI for review
- Web search grounding via SearXNG (toggle in toolbar, enriches prompts)
- Responsive preview with device size selector (Full/Desktop/Tablet/Mobile)
- /api/search proxy route
Fixes:
- Model selector text color now white on dark theme
- Post-coding button text overflow (shorter labels + min-w-0)
- Duplicate activateArtifact button suppressed when action row shows
