Migrate to ONNX with modern uv/Gradio 5 stack

- Export FastAI model to ONNX format (335MB)
- Replace PyTorch/FastAI dependencies with onnxruntime
- Upgrade to Gradio 5 with modern Blocks interface
- Modular architecture with stashtag package
- Clean requirements.txt for HuggingFace Spaces deployment
- 4 core dependencies vs 100+ in original version

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

requirements.txt

@@ -0,0 +1,4 @@
+onnxruntime>=1.15.0
+gradio>=5.0.0
+pillow>=9.0.0
+numpy>=1.24.0