Auth for web apps

I am currently planning a „companion app“ for Dynalist. It‘s going to mainly show lists of tasks based on due dates and tags. Basically filters on steroids plus some comfort functions for managing tasks.

(I am building this only for myself and have no intentions of making it a „product“, but might make it public on Github.)

I was wondering if you had any input on how I could handle logging in.

My current best plan: Simply put the API key and my chosen username/password (hashed) in the configuration of my serverside code. Since it‘s going to be essentially just for me, that should suffice for now. And it saves me from having to handle a user database.

But is there a way to make this better? Ideally I would make this available to all, but if that means that the users would have to enter their API keys into my app, that would be pretty… inelegant. (If the TOS even permit such a thing.)

So I‘m guessing this is pretty much it for the time being until something like an OAuth login is implemented. Or am I missing something?