feat: Round 24 - Klassenlehrer management, vice principal, exam calendar, student portal exams

- Klassenlehrer management: Assign/change responsible teacher, privilege badges
- Vice principal management: Assign/remove VP role, admins list
- Calendar exam integration: Exam countdown, print calendar, exam filter
- Student portal: Exams tab with countdown, AI study tips, virtual character
- Dashboard: Klassenlehrer section with pending illness/communications
- API: PUT /api/users/role for role management
- API: Enhanced classes GET to include responsibleTeacher
- 90+ new i18n keys

src/lib/api.ts

@@ -155,10 +155,13 @@ export interface ClassGroup {
   schoolType: string;
   school: { id: string; name: string };
   schoolYear: { id: string; label: string };
+  responsibleTeacherId?: string | null;
+  responsibleTeacher?: { id: string; firstName: string; lastName: string; email: string } | null;
   teachers: Array<{ id: string; userId: string; role: string; user: { id: string; firstName: string; lastName: string; email: string } }>;
   studentCount?: number;
+  assessmentCount?: number;
   teacherList?: Array<{ id: string; firstName: string; lastName: string; teacherRole: string }>;
-  _count?: { enrollments?: number; competencyAssignments?: number; [key: string]: unknown };
+  _count?: { enrollments?: number; competencyAssignments?: number; assessments?: number; [key: string]: unknown };
 }
 
 export function fetchClasses(schoolId?: string, schoolYearId?: string): Promise<ClassGroup[]> {