Telegram Auto Join Start Bot

I need a small Telegram utility that runs from one existing account, fires up on its own, and immediately joins a specific channel that I will provide. Both functions—auto-starting and auto-joining—have to be baked in; there is no verification step or user prompt in the flow.

Python with Telethon, Pyrogram, or a comparable library is fine as long as the result is reliable and easy for me to deploy on a VPS. Please include:

• the full, well-commented source code
• a short read-me showing the one-time setup (API keys, channel ID, start command) and the single command or service file needed to keep it running

If you have questions about the channel details or API credentials, let me know so we can get this running quickly.