Improve modals

[hmpf]

See

• [x] #1229 (for modals)
• [x] #1228
• [ ] #1227
• [ ] #1224
• [ ] #1206
• [ ] #1204
• [x] #1201
• [x] #1051
• [ ] #1047

For modals specifically:

• [ ] #1062
• [ ] #1059

[hmpf]

I suspect much will be improved/clearer by getting #1206 done

[hmpf]

To delete when done:

• [ ] htmx/timeslot/_delete_timeslot_confirm_dialog.html
• [ ] htmx/destination/_delete_form.html