feat: Reminder Manager + Schattenmarkt-Freigabe + mock data overhaul

- Add Reminder Manager page (/supply/reminder-manager) with KPI bar,
  filter bar, list/card feed, and detail drawer (7 sections incl.
  activity log, snooze, complete, dismiss actions)
- Add Schattenmarkt-Freigabe toggle on PropertyDetailView: Verwaltung
  can opt-in properties for early market exposure before contract expiry
- Auto-generate FutureSignal cards via useSchattenmarktSignals hook
  when leaseEndDate - leadTimeMonths <= MOCK_TODAY
- Fix useUnifiedResults: use property.resultType as fallback (was
  defaulting everything to VERIFIED_PORTFOLIO)
- Fix demand Results: hide VERIFIED_PORTFOLIO from non-manager users
  even when showOwnProperties toggle was previously enabled
- Fix AppShell: redirect to allowed workspace on user role switch
- Fix 3 wrong match scores (match-002: 93→62, match-009: 86→55,
  match-017: 87→52)
- Add 7 new match records (match-050–056) for need-001, need-002,
  need-011
- Add need-011 (Retail Bern Innenstadt)
- Add prop-031–036 (EXTERNAL_MARKET / MAISON_WORK / FUTURE_AVAILABILITY)
- Fix duplicate image URLs across all properties
- Add signal-011 (Bern Altstadt, Mode Boutique) + propertyId to
  signal-001

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

src/components/supply/ReminderHeader.tsx

@@ -0,0 +1,45 @@
+import { Box, Typography, Button } from '@mui/material'
+import { Plus } from 'lucide-react'
+import { useReminderStore } from '../../stores/reminderStore'
+
+export function ReminderHeader() {
+  const { setDrawerOpen, setSelectedId } = useReminderStore()
+
+  function handleCreate() {
+    setSelectedId(null)
+    setDrawerOpen(true)
+  }
+
+  return (
+    <Box
+      sx={{
+        bgcolor: 'white',
+        borderBottom: '1px solid',
+        borderColor: 'divider',
+        px: 3,
+        py: 2,
+        display: 'flex',
+        alignItems: 'flex-start',
+        justifyContent: 'space-between',
+      }}
+    >
+      <Box>
+        <Typography variant="h5" sx={{ fontWeight: 700, color: '#1e293b' }}>
+          Reminder Manager
+        </Typography>
+        <Typography variant="body2" color="text.secondary">
+          Fristen, Vertragsereignisse und Aufgaben für Ihr Portfolio
+        </Typography>
+      </Box>
+      <Button
+        variant="contained"
+        size="small"
+        startIcon={<Plus size={16} />}
+        onClick={handleCreate}
+        sx={{ textTransform: 'none', fontWeight: 600 }}
+      >
+        Reminder erstellen
+      </Button>
+    </Box>
+  )
+}