feat: Admin-Toggle für mobile Zeiterfassung

Backend:
- Company.mobile_stamping_enabled (BOOLEAN DEFAULT TRUE)
- CompanyOut + CompanyUpdate: neues Feld
- Migration 0027: companies.mobile_stamping_enabled

Frontend Desktop (CompanySettingsPage):
- Abschnitt 'Mobile-Ansicht' mit Toggle-Switch
- Speichert via PATCH /companies/me

Frontend Mobile (MobileStampScreen):
- Lädt mobile_stamping_enabled aus GET /companies/me
- Deaktiviert: Hinweis-Banner statt Buttons
  ('Einstempeln nicht verfügbar – bitte Kiosk/Desktop nutzen')
- Aktiviert: normales Verhalten

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/mobile/MobileStampScreen.tsx

@@ -9,6 +9,10 @@ interface TodayStatus {
   break_minutes?: number
 }
 
+interface CompanySettings {
+  mobile_stamping_enabled: boolean
+}
+
 interface TimeEntryWithWarnings {
   entry: { id: string }
   warnings: string[]
@@ -64,6 +68,7 @@ function fmtTime(iso: string | null): string {
 export function MobileStampScreen() {
   const [dashboard, setDashboard] = useState<TodayStatus | null>(null)
   const [balance, setBalance] = useState<BalanceResponse | null>(null)
+  const [stampingAllowed, setStampingAllowed] = useState(true)
   const [loading, setLoading] = useState(true)
   const [stamping, setStamping] = useState(false)
   const [error, setError] = useState<string | null>(null)
@@ -78,12 +83,14 @@ export function MobileStampScreen() {
     setError(null)
     try {
       const monday = getMondayOfCurrentWeek()
-      const [dash, bal] = await Promise.all([
+      const [dash, bal, company] = await Promise.all([
         api.get<TodayStatus>('/dashboard/me'),
         api.get<BalanceResponse>(`/time/balance/me?period_start=${monday}`),
+        api.get<CompanySettings>('/companies/me'),
       ])
       setDashboard(dash)
       setBalance(bal)
+      setStampingAllowed(company.mobile_stamping_enabled ?? true)
     } catch (e: unknown) {
       setError(e instanceof Error ? e.message : 'Fehler beim Laden')
     } finally {
@@ -190,6 +197,20 @@ export function MobileStampScreen() {
         </div>
       )}
 
+      {/* Stempeln deaktiviert */}
+      {!stampingAllowed && (
+        <div className='bg-amber-50 border border-amber-200 rounded-xl px-4 py-4 flex gap-3 items-start'>
+          <span className='text-xl mt-0.5'>🔒</span>
+          <div>
+            <p className='text-sm font-semibold text-amber-800'>Einstempeln nicht verfügbar</p>
+            <p className='text-xs text-amber-700 mt-0.5'>
+              Dein Unternehmen hat die Zeiterfassung über die mobile Ansicht deaktiviert.
+              Bitte nutze das Kiosk-Terminal oder die Desktop-Version.
+            </p>
+          </div>
+        </div>
+      )}
+
       {/* Status-Karte */}
       <div className='bg-white rounded-2xl border border-gray-200 shadow-sm px-5 py-5 flex flex-col items-center gap-3'>
         {/* Status-Label */}
@@ -232,8 +253,8 @@ export function MobileStampScreen() {
           </div>
         )}
 
-        {/* Haupt-Button */}
-        {!isOpen ? (
+        {/* Haupt-Button – nur wenn Stempeln erlaubt */}
+        {stampingAllowed && !isOpen ? (
           <button
             onClick={stampIn}
             disabled={stamping}
@@ -243,7 +264,7 @@ export function MobileStampScreen() {
               <span className='animate-spin rounded-full h-7 w-7 border-4 border-white border-t-transparent' />
             ) : 'EINSTEMPELN'}
           </button>
-        ) : isOnBreak ? (
+        ) : stampingAllowed && isOnBreak ? (
           <button
             onClick={breakEnd}
             disabled={stamping}
@@ -253,7 +274,7 @@ export function MobileStampScreen() {
               <span className='animate-spin rounded-full h-7 w-7 border-4 border-white border-t-transparent' />
             ) : 'PAUSE BEENDEN'}
           </button>
-        ) : (
+        ) : stampingAllowed ? (
           <button
             onClick={stampOut}
             disabled={stamping}
@@ -265,8 +286,10 @@ export function MobileStampScreen() {
           </button>
         )}
 
+        ) : null}
+
         {/* Sekundärer Button: Pause starten */}
-        {isOpen && !isOnBreak && (
+        {stampingAllowed && isOpen && !isOnBreak && (
           <button
             onClick={breakStart}
             disabled={stamping}