I want a lightweight bot that can fetch online videos and save them locally in MP4 every time. I should be able to point it at the source—whether that ends up being YouTube, Vimeo, Instagram, or any other site we agree on—and have the file appear on my machine ready to watch or archive. Key points I care about: • MP4 is the mandatory output format. • Code needs to be clean, well-commented, and simple for me to run on my own system after delivery. • Platform coverage can stay flexible; we will final-check the target sites together before you package the solution. If you have a preferred language or framework for handling downloads (Python + pytube/pytube3, Node + ytdl-core, etc.), let me know; otherwise pick whatever gets the job done reliably. Please include a quick outline of how you will manage any rate limits or platform restrictions so I can see the approach before we start.