I built something very, very similar for a client to post their content on schedule to about 9 different social networks. It was my first major vibe-coded app -- I normally vibe-code a function or small apps. Took about two hours with Claude [0] by just building up the functionality in layers, testing each layer as we went. If I'd rawdogged it, 2022-style, it would probably have taken me a month to write.

It's been running flawlessly for months without a single error. In fact, spooky good. I still feel nervous about it, though and check it every morning.

It is built mostly as a web app in .NET 10 Razor with SQLite db.

The APIs for the social networks are the hazy bit. As OP mentions, some are badly documented. Some are a pain to get access to. I was using a driven browser to post to Twitter, but they opened their API recently, which was nice.

[0] I used Claude in Github Copilot, so total cost was less than the $10/month in credits.