docs: Add live HuggingFace Space demo link to README

Fix: Replace invalid buttons param with show_copy_button=True

Fix: Wrap GoogleFont in list for gradio 4.44.0 compatibility

Fix: Pin gradio==4.44.0 + huggingface_hub==0.25.2 for compatibility

Fix: Add HuggingFace Space YAML config to README

🤖 Add README, update .gitignore — AI Code Debugger Agent

Initial commit: AI Code Debugger with multi-provider fallback and professional UI