Design follow-ups for absence overview page

The following discussion from !363 (merged) should be addressed:

• @yuha started a discussion: (+1 comment)

  • switches too much height
  • mobile design is not vorhanden
  • show only lessons with absences by default
  • align the absencereason chips correctly
  • align checkbox to warndreieck
  • mark-as-box should be more compact
  • make everything more compact 😠

@yuha Please check that all issues are solved.