Switch to file upload instead of YouTube download (YouTube blocks cloud servers)

Pin gradio==5.12.0, add explicit api_name to fix /predict 500

Fix: add Invidious fallback for downloads, remove gr.Examples crash

Fix: download kits to /tmp (writable by UID 1000)

Switch to Docker SDK for faster builds and layer caching

Move kits to HF dataset repo, download on startup, sync all latest code

SampleFlip: AI beat generator