This takes part of the work being done in #96 that was reverted but still useful.
Note Tailwind and Fresh weren't upgraded because there's no security vulnerability in either, and I have found the new versions to be worse in performance. Thos will likely stay at those fixed versions going forward.
This refactors the data handlers into a more standard/understood model-like architecture, to prepare for a new, more robust config system.
It also fixes a problem with creating new Notes and uploading new Photos via the web interface (related to #58).
Finally, it speeds up docker builds by sending in less files, which aren't necessary or will be built anyway.
This is all in preparation to allow building #13 more robustly.
