App’s are not associated with any specific user. Just because you’re the developer of the app doesn’t mean you’ve granted it any special permissions to access your account, so you need to go through the OAuth process like any other user would to get a User Token with permissions for whatever it is you want to do.
If it’s just for yourself, set the Redirect URI to localhost, go through the Auth Code flow process once, and even if you’re not hosting a web server and 404 you’ll still get the code param in the URL, which you can then exchange for an Access Token and Refresh Token. As long as you store those tokens in some what (database, a file, whatever) you can refresh your tokens programmatically without needing any web server, and no need to go through the OAuth process again.