feat: Mietvertrag hinterlegen pro Objekt (Link + Bezeichnung)

- Property.leaseContractUrl? + leaseContractName? im Domain
- PropertyDetailOverview: Mietvertrag-Block in "Miet- & Mieterinformationen"
  — View-Modus: Öffnen-Button oder "Noch kein Vertrag"-Hinweis
  — Edit-Modus: URL-Feld + Bezeichnungsfeld (gespeichert via updateProperty)
- ReminderDetailDrawer: Mietvertrag-Link im "Objekt"-Abschnitt
  (lädt Property über usePropertyById)

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

src/components/supply/ReminderDetailDrawer.tsx

@@ -12,9 +12,10 @@ import {
   FormControlLabel,
   Tooltip,
 } from '@mui/material'
-import { X, MapPin, Calendar, DollarSign, Eye, Activity } from 'lucide-react'
+import { X, MapPin, Calendar, DollarSign, Eye, Activity, FileText, ExternalLink } from 'lucide-react'
 import { useReminderStore } from '../../stores/reminderStore'
 import { useReminder, useCompleteReminder, useDismissReminder, useSnoozeReminder } from '../../hooks/useReminders'
+import { usePropertyById } from '../../hooks/useProperties'
 import { ReminderPriorityBadge } from './ReminderPriorityBadge'
 import { ReminderTypeBadge } from './ReminderTypeBadge'
 import { ReminderDaysIndicator } from './ReminderDaysIndicator'
@@ -24,6 +25,7 @@ import { SHADOW_RISK_COLOR, SHADOW_RISK_LABEL, STATUS_CHIP_COLOR, STATUS_LABEL,
 export function ReminderDetailDrawer() {
   const { selectedId, drawerOpen, setDrawerOpen, setSelectedId } = useReminderStore()
   const { data: reminder } = useReminder(selectedId ?? '')
+  const { data: reminderProperty } = usePropertyById(reminder?.propertyId ?? '')
   const complete = useCompleteReminder()
   const dismiss = useDismissReminder()
   const snooze = useSnoozeReminder()
@@ -101,6 +103,27 @@ export function ReminderDetailDrawer() {
                 </Typography>
                 <Typography variant="caption" color="text.secondary">Mieter: {reminder.tenantName}</Typography>
                 <Typography variant="caption" color="text.secondary">Fläche: {reminder.areaSqm.toLocaleString('de-CH')} m²</Typography>
+                {reminderProperty?.leaseContractUrl ? (
+                  <Box sx={{ display: 'flex', alignItems: 'center', gap: 0.75, mt: 0.5 }}>
+                    <FileText size={12} color="#1e3a5f" />
+                    <Button
+                      size="small"
+                      variant="outlined"
+                      endIcon={<ExternalLink size={10} />}
+                      href={reminderProperty.leaseContractUrl}
+                      target="_blank"
+                      rel="noopener noreferrer"
+                      sx={{ textTransform: 'none', fontSize: '0.68rem', py: 0.125, px: 0.75, borderColor: '#cbd5e1', color: '#1e3a5f' }}
+                    >
+                      {reminderProperty.leaseContractName ?? 'Mietvertrag'}
+                    </Button>
+                  </Box>
+                ) : (
+                  <Box sx={{ display: 'flex', alignItems: 'center', gap: 0.5, mt: 0.5 }}>
+                    <FileText size={12} color="#cbd5e1" />
+                    <Typography variant="caption" sx={{ color: '#cbd5e1' }}>Kein Mietvertrag hinterlegt</Typography>
+                  </Box>
+                )}
               </Box>
             </Box>