Notes improvement + theme settings

[SO9010]

I want to start this PR by saying thanks for creating a great service and for having it open source, that has made be hugely happy. I have started to degoogle, and I have found filen as the best alternative!

However, this app is the only thing that's forcing me to still have ties with Google, mainly being the fact that the notes section on the app is not even comparable for quick note-taking.

In this PR I am proposing and have implemented my favourite thing that I felt was missing filen notes, masonary grids and a floating plus button. Having the plus button at the top feels very much like web ui thinking rather than mobile UI.

Additionally, in this PR I did a few other changes as they helped me debug:
1: Add an option to change the theme through settings
2: Make it so the icons on the notes page follows the dark theme correctly

The feature is toggleable at the top in the right hand corner where the + used to be. I have only got access to an android device so have only tested on there.

If there is anything you disagree with or would like to change, please feel free to!

There are also other things that I will create a PR to fix, for example search button changes place on every page, images doesnt have a default directory to look through, and I think the photos' section would strongly benefit from a time scale on the scrolling otherwise it is a bit overwhelming.

Addionally things like image & audio notes and alerts would be great for me to add but are at the bottom of my list!

Another thing I would like to implement, but may need help with would be allowing offline usage for the product!

Thanks again for making such a good product and I am excited to continue helping to make this product as good as it possibly can be! I will also wait for your review or go ahead before working on any of these other mentioned things

[SO9010]

Heya, just wandering if this has been seen by anyone?

[DanielProg39]

Amazing work, maybe we should ping @Dwynr to take a look