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/CompanySettingsPage.tsx

@@ -53,6 +53,8 @@ export function CompanySettingsPage() {
   const [pnRequired, setPnRequired] = useState(false)
   const [pnMode, setPnMode] = useState<'manual' | 'auto'>('manual')
   const [pnNext, setPnNext] = useState(1)
+  // Mobile
+  const [mobileStamping, setMobileStamping] = useState(true)
   // Busylight
   const [blStatus, setBlStatus] = useState<{ configured: boolean; created_at: string | null } | null>(null)
   const [blPlaintext, setBlPlaintext] = useState<string | null>(null)
@@ -76,6 +78,7 @@ export function CompanySettingsPage() {
       setPnRequired(c.personnel_number_required ?? false)
       setPnMode(c.personnel_number_mode ?? 'manual')
       setPnNext(c.personnel_number_next ?? 1)
+      setMobileStamping((c as CompanyOut & { mobile_stamping_enabled?: boolean }).mobile_stamping_enabled ?? true)
     }).catch(() => {})
     api.get<{ configured: boolean; created_at: string | null }>('/companies/me/busylight-token')
       .then(setBlStatus)
@@ -143,6 +146,7 @@ export function CompanySettingsPage() {
         personnel_number_required: pnRequired,
         personnel_number_mode: pnMode,
         personnel_number_next: pnNext,
+        mobile_stamping_enabled: mobileStamping,
       })
       setCompany(updated)
       setSaved(true)
@@ -519,6 +523,37 @@ export function CompanySettingsPage() {
           </div>
         )}
 
+        {/* Mobile-Einstellungen */}
+        <div className="bg-white rounded-xl shadow-sm border border-gray-200 p-6 space-y-4">
+          <div className="flex items-center gap-2">
+            <span className="text-lg">📱</span>
+            <h2 className="font-semibold text-gray-700">Mobile-Ansicht</h2>
+          </div>
+          <div className="flex items-center justify-between gap-4">
+            <div>
+              <p className="text-sm font-medium text-gray-800">Einstempeln über Mobile erlauben</p>
+              <p className="text-xs text-gray-500 mt-0.5">
+                Wenn deaktiviert, sehen Mitarbeiter unter <code className="bg-gray-100 px-1 rounded">/mobile</code> keinen Stempel-Button.
+                Nützlich wenn Zeiterfassung nur über Kiosk-Terminals erfolgen soll.
+              </p>
+            </div>
+            <button
+              type="button"
+              disabled={!isAdmin}
+              onClick={() => setMobileStamping(v => !v)}
+              className={`relative inline-flex h-6 w-11 flex-shrink-0 rounded-full border-2 border-transparent transition-colors duration-200 focus:outline-none disabled:opacity-50 disabled:cursor-not-allowed ${
+                mobileStamping ? 'bg-blue-600' : 'bg-gray-300'
+              }`}
+            >
+              <span
+                className={`pointer-events-none inline-block h-5 w-5 rounded-full bg-white shadow transform transition-transform duration-200 ${
+                  mobileStamping ? 'translate-x-5' : 'translate-x-0'
+                }`}
+              />
+            </button>
+          </div>
+        </div>
+
         {/* Firmen-Info (readonly) */}
         {company && (
           <div className="bg-white rounded-xl shadow-sm border border-gray-200 p-6">