Refactor of the application layout and database system - POTENTIAL BREAKING CHANGE

[seapagan]

I have merged PR #127, which refactors the code layout to put everything code-related into an app subdirectory. The tests have been updated, and they all pass OK. I have meant to do this for a while, and it's better now before it gets more complicated.

However, this may be a BREAKING CHANGE for those who have already customized the app with extra files.

Note that you may have to delete the original empty folders on an existing checkout manually. This will be the last (planned!) layout change like this 🤞

[seapagan]

Since I have probably broken backward compatibility due to the above change , I may as well break it for the database as well 🤣

See #125 (comment)

Basically, I want to change to using SQLAlchemy 2.0 and their own Async system as the databases package seems not to be actively maintained. I'll have a think about this and open a PR when ready.

[seapagan]

I'm looking to merge the entire develop branch into main, probably today or tomorrow, depending on other workloads.

I will then create a new 0.4.x tag and release that will contain the last version of the previous system, with a few fixes and updated dependencies.

There will also be a 'gatekeeper' function applied to stop running the server until the user has read the update notes 😝