fix: BerichtDialog, images, and add property number + floor/unit structure

- BerichtDialog: conditionally mount instead of always-mounted with
  open prop; starts in 'generating' state immediately on open
- Images: fix all 6 wrong VERIFIED_PORTFOLIO and EXTERNAL_MARKET photos
  to match spec per assetType (OFFICE/RETAIL/LOGISTICS/PRODUCTION/MIXED)
- Domain: add PropertyUnit interface + propertyNumber field to Property
- Mock data: propertyNumber + units[] for prop-001/007/012/013
- UI: Stockwerkstruktur section in Übersicht tab (floor/unit table with
  availability, tenant, area); Objekt-Nr. shown below key metrics

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

src/domain/property.ts

@@ -82,6 +82,20 @@ export interface SoftFactors {
   infrastructureNotes?: string
 }
 
+// ── Floor / Unit structure ────────────────────────────────────────────────────
+
+export interface PropertyUnit {
+  id: string
+  floorLevel: number        // 0=EG, 1=1.OG, -1=UG
+  unitLabel?: string        // e.g. "Ost", "West", "Einheit A"
+  areaSqm: number
+  available: boolean
+  rentPricePerSqm?: number
+  currentTenant?: string
+  leaseTerm?: string
+  leaseEndDate?: string
+}
+
 // ── Property ──────────────────────────────────────────────────────────────────
 
 export interface Property {
@@ -129,6 +143,9 @@ export interface Property {
   description?: string
   images?: string[]
 
+  propertyNumber?: string
+  units?: PropertyUnit[]
+
   leaseTerm?: string
   leaseStartDate?: string
   leaseEndDate?: string