Update app.py

Add all 38 yolo26 prebackbone_samples as Gradio examples

Fix HF unstyled UI: disable SSR, stop pip-overriding Gradio

Fix HF Space unstyled UI: stop overriding Gradio proxy settings

Fix HF UI: restore gr.Interface layout instead of bare Blocks

RefDiffNet: standalone A11_CA prebackbone Gradio Space

Fix Gradio schema bug: Interface+filepath, gradio-client>=1.4

Fix Gradio 4.49 pil images and HF launch (no share)

RefDiffNet: A11_CA prebackbone demo (clean history, no images in git)