refactor: split PropertyDetailView (998→192 lines) and MatchDetail (464→236 lines)

PropertyDetailView.tsx extracted into 5 focused components:
- PropertyDetailHelpers: Field, FieldGrid, SectionTitle, floorLabel
- UnitStructurePanel: floor structure with unit matching
- PreMarketPanel: schattenmarkt release controls
- PropertyDetailOverview: overview tab content
- MatchabilityTabPanel: need matches tab

MatchDetail.tsx extracted into 2 focused components:
- MatchDetailHero: image/map, header, key facts strip
- MatchDetailPropertySections: Preis/Hauptangaben/Eigenschaften/etc.

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

src/components/supply/PropertyDetailHelpers.tsx

@@ -0,0 +1,41 @@
+import { Box, Typography } from '@mui/material'
+import type { PropertyUnit } from '../../domain/property'
+
+export function floorLabel(u: PropertyUnit): string {
+  if (u.floorLevel === 0) return 'EG'
+  if (u.floorLevel < 0) return `UG${Math.abs(u.floorLevel)}`
+  return `${u.floorLevel}.OG`
+}
+
+export function Field({ label, value }: { label: string; value?: string | number | boolean | null }) {
+  return (
+    <Box sx={{ mb: 1.5 }}>
+      <Typography variant="caption" color="text.secondary" sx={{ display: 'block', lineHeight: 1 }}>
+        {label}
+      </Typography>
+      {value !== undefined && value !== null && value !== '' ? (
+        <Typography variant="body2" sx={{ fontWeight: 500, mt: 0.25 }}>
+          {typeof value === 'boolean' ? (value ? 'Ja' : 'Nein') : String(value)}
+        </Typography>
+      ) : (
+        <Typography variant="body2" color="text.disabled" sx={{ mt: 0.25 }}>—</Typography>
+      )}
+    </Box>
+  )
+}
+
+export function FieldGrid({ children }: { children: React.ReactNode }) {
+  return (
+    <Box sx={{ display: 'grid', gridTemplateColumns: '1fr 1fr', gap: 0.5 }}>
+      {children}
+    </Box>
+  )
+}
+
+export function SectionTitle({ title }: { title: string }) {
+  return (
+    <Typography variant="subtitle2" sx={{ fontWeight: 600, mb: 1.5, mt: 0.5 }}>
+      {title}
+    </Typography>
+  )
+}