Implemented transaction notes feature

In the last devlog I made a box for adding notes to a transaction.

Now I created a backend for it & frontend logic to make it work!

I added some more API endpoints, to get a note and set/update a note, and a transactions summary endpoint which is like the transactions endpoint but doesn’t give the unused information and says whether a transaction has a note or not (not the note itself). This allows the list of transactions to show a note icon on the transactions in the list. you can then click on them to view/edit the note.