It really depends on whether those reusable apps are actually going to be reused outside of the project or not?
The only reason you might need it in a different repo is if other projects with seperate repos might need to use it. But you can always split it out later. Making a git repo is cheap so it's one of those things you can do later if it becomes necessary. Making things complicated up front is just going to frustrate you later so feel free to wait till you know it's necessary
YAGNI it's for more than just code.
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