Usability fixes

[mtotschnig]

The following usability problems were identified during my participation at a workshop at the FOSS Backstage Design Conference: https://program.foss-backstage.de/ux24/talk/NG7QEV/

• [x] On Tag screen, there is no representation of the empty state
• [x] Before user has entered any data, commands that need data to operate on should not be offered in the menu: Search, Export, Print
• [ ] Not all default category icons might make sense
• [x] If user deletes the last account, there is no easy way back to have an active account again.
• [x] If user calls "New transfer" before having created a second account, we should offer to create the missing account.
• [ ] Delete operations are guarded by a confirmation dialog, but there is no Undo affordance.
• [ ] The swipe gesture allowing to navigate between accounts is in conflict with the the system back gesture.