Add chat editing + 3D garment preview

New features:
- Chat & Edit tab: edit patterns with natural language
- 3D garment preview using Plotly (interactive rotate/zoom)
- VLM-powered edits via Qwen3.5/Gemma4/Kimi K2.5
- Rule-based edit fallback for common modifications
- All tabs now show both 2D pattern and 3D preview

requirements.txt

@@ -4,3 +4,4 @@ numpy
 scipy
 Pillow
 requests
+plotly