fix: various bugs

[MaSch0212]

• navigate back to event after deleting a timeslot
• error when deleting timeslot that has been selected as fallback by a player
• use same docker tag for build and push
• player event state is not updated when changing events
  • Before the fix admins had to reload the page to see the event updates on the start page.
• load correct locale for PrimeNG
• infinite loading circle if login token in local storage is invalid
• reset controls when registration change fails
• users are displayed as "empty" in dropdowns

Closes: #30, #32, #33, #39, #45