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.
If you're using a reverse proxy like Cloudflare Tunnels, you can now set `CONFIG_SKIP_COOKIE_DOMAIN_SECURITY="true"` to avoid login issues.
Also makes some UX tweaks to Expenses, and fixes a style issue for Chrome in Windows (#44).
Fixes#43Fixes#44
