fix: correct uvicorn startup path for HuggingFace Spaces

- Run uvicorn from /app directory instead of /app/backend
- This allows proper Python module imports (backend.*)
- Fixes ModuleNotFoundError in HuggingFace deployment

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

start.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 
-# Start FastAPI backend in the background
-cd /app/backend && uvicorn main:app --host 0.0.0.0 --port 8000 &
+# Start FastAPI backend in the background (run from /app so imports work)
+cd /app && uvicorn backend.main:app --host 0.0.0.0 --port 8000 &
 
 # Start Next.js frontend on port 7860 (required by Hugging Face)
-cd /app/frontend && npm start -- -p 7860
+cd /app/frontend && npm start -- -p 7860