implemented absence report module with form validation, prefill support, and API integration

lib/storage/modules_settings.g.dart

@@ -39,4 +39,5 @@ const _$ModulesEnumMap = {
   Modules.gradeAveragesCalculator: 'gradeAveragesCalculator',
   Modules.holidays: 'holidays',
   Modules.marianumDates: 'marianumDates',
+  Modules.absenceReport: 'absenceReport',
 };