Use synchronous function with @spaces.GPU for ZeroGPU compatibility

Add full /download_tg endpoint implementation in app.py

Add /download_tg endpoint with FastAPI and Gradio mount

Add @spaces.GPU decorator to app.py

Fix huggingface_hub import error for gradio

Minimal stable gradio config

Fix app.py with standard gradio interface

Switch back to Gradio SDK for ZeroGPU compatibility