Improve journal UX

[cdubz]

The journal UX is clunky. Two key changes that would help a lot —

1. Immediate feedback on day macros effect of making a change.
2. Ability to quickly edit existing entries.

The current system was designed to be flexible with respect to added data for multiple days at once but that seems like an edge case that isn’t worth building for. Implementing these improvements should be easier if that feature can be sacrificed (or at least deprioritized).

[spusuf]

Happy to contribute to this, would you like an updated UX added as a PR? Also would you like me to use HTML + CSS to create a mockup site where you can add any backend yourself?

[spusuf]

I'll look into modernising the interface, adding a dashboard for totals and historical tracking, themes, etc.