Add gunicorn with 2 workers for better concurrent request handling

Add retry logic, HTML error detection, and increased timeout for PixVerse API calls

Update category matching to 4 types: Ai BF, Ai GF, Ai Hug Video, Ai Kiss Video

Add Hugging Face Space configuration

Add .gitignore

Initial commit: PixVerse Video Generator API with Firebase auth, MongoDB tracking, and Digital Ocean storage