i18n: Fix 19 more hardcoded English strings in admin pages and components

Fixed:
- compliance-overview: Compliance Monitoring Dashboard, Onboarding Status, Data Retention Policies, Active Policies, Consultation Log
- exam-proctoring: Exam Proctoring, Active Sessions, Total Sessions
- signage: Emergency Signage, Normal option
- compliance-wizard: Data Retention Periods, Consultation Checklist, Compliance Setup Complete
- dashboard-customizer: Add Widget
- data-import-export: Data Management Best Practices, Export data regularly
- district-management: Access Denied
- exam-session-monitor: Exam Mode Active
- professional-calendar: Fixed 'Create Neues Ereignis' typo
- sidebar: Toggle Sidebar

All admin pages and shared components now fully German.

src/app/admin/compliance-overview/page.tsx

@@ -56,7 +56,7 @@ export default function ComplianceDashboard() {
   return (
     <div className="space-y-8 p-8">
       <div>
-        <h1 className="text-3xl font-bold text-slate-900">Compliance Monitoring Dashboard</h1>
+        <h1 className="text-3xl font-bold text-slate-900">Compliance-Monitoring-Dashboard</h1>
         <p className="text-slate-600 mt-2">
           Track your school&apos;s data protection compliance status and document management
         </p>
@@ -73,7 +73,7 @@ export default function ComplianceDashboard() {
                 <AlertCircle className="w-8 h-8 text-yellow-600" />
               )}
               <div>
-                <p className="text-sm text-slate-600">Onboarding Status</p>
+                <p className="text-sm text-slate-600">Onboarding-Status</p>
                 <p className="font-semibold text-slate-900">
                   {data.status?.onboardingCompleted ? "Complete" : "Pending"}
                 </p>
@@ -87,7 +87,7 @@ export default function ComplianceDashboard() {
             <div className="flex items-center gap-3">
               <FileText className="w-8 h-8 text-blue-600" />
               <div>
-                <p className="text-sm text-slate-600">Data Retention Policies</p>
+                <p className="text-sm text-slate-600">Datenaufbewahrungsrichtlinien</p>
                 <p className="font-semibold text-slate-900">
                   {data.policiesConfigured} / {data.policiesReviewed} reviewed
                 </p>
@@ -124,7 +124,7 @@ export default function ComplianceDashboard() {
       {/* Data Retention Policies */}
       <Card>
         <CardHeader>
-          <CardTitle>Active Data Retention Policies</CardTitle>
+          <CardTitle>Aktive Datenaufbewahrungsrichtlinien</CardTitle>
           <CardDescription>
             Configured retention periods for each data category
           </CardDescription>
@@ -170,7 +170,7 @@ export default function ComplianceDashboard() {
       {data.consultations.length > 0 && (
         <Card>
           <CardHeader>
-            <CardTitle>Consultation Log</CardTitle>
+            <CardTitle>Beratungsprotokoll</CardTitle>
             <CardDescription>
               Staff and parent body consultations per module
             </CardDescription>

src/app/admin/exam-proctoring/page.tsx

@@ -111,7 +111,7 @@ export default function ExamProctoringPage() {
     <div className="space-y-6">
       <div className="flex items-center justify-between">
         <div>
-          <h1 className="text-3xl font-bold text-gray-900">Exam Proctoring</h1>
+          <h1 className="text-3xl font-bold text-gray-900">Prüfungsüberwachung</h1>
           <p className="text-gray-600 mt-1">Monitor active exam sessions and suspicious activity</p>
         </div>
       </div>
@@ -121,7 +121,7 @@ export default function ExamProctoringPage() {
         <div className="bg-white rounded-lg border border-gray-200 p-4">
           <div className="flex items-center justify-between">
             <div>
-              <p className="text-gray-600 text-sm font-medium">Active Sessions</p>
+              <p className="text-gray-600 text-sm font-medium">Aktive Sitzungen</p>
               <p className="text-2xl font-bold text-gray-900 mt-1">{activeCount}</p>
             </div>
             <Clock className="w-8 h-8 text-blue-500" />
@@ -141,7 +141,7 @@ export default function ExamProctoringPage() {
         <div className="bg-white rounded-lg border border-gray-200 p-4">
           <div className="flex items-center justify-between">
             <div>
-              <p className="text-gray-600 text-sm font-medium">Total Sessions</p>
+              <p className="text-gray-600 text-sm font-medium">Sitzungen gesamt</p>
               <p className="text-2xl font-bold text-gray-900 mt-1">{sessions.length}</p>
             </div>
             <Eye className="w-8 h-8 text-purple-500" />

src/app/admin/signage/page.tsx

@@ -80,7 +80,7 @@ export default function SignageAdminPage() {
     <div className="space-y-6">
       <div className="flex items-center justify-between">
         <div>
-          <h1 className="text-3xl font-bold text-gray-900">Emergency Signage</h1>
+          <h1 className="text-3xl font-bold text-gray-900">Notfall-Digital-Schild</h1>
           <p className="text-gray-600 mt-1">Manage displays, messages, and emergency alerts</p>
         </div>
         <Button onClick={() => setShowNewMessage(true)} size="lg" className="gap-2">