feat: Anfragencenter Parts A–E — read/unread, prep wizard, offer flow, report preview

- Part A: Replace InquiryStatus badges with WhatsApp-style unread indicators
  (isRead, unreadCount, lastReadAt on Inquiry; markThreadAsRead in service + hook)
- Part B: RelatedPropertyCardPanel — reposition "Objekt ansehen", add "Weitere
  Matches" section via matchService.getAdditionalMatchesForInquiry
- Part C: PreparationWizard 4-step dialog — property selection, report generation
  progress, field editing + ReportObjectFieldSelector, PDF preview + finalize
- Part D: OfferCreationWizard 4-step dialog triggered from first tenant message —
  data capture, field editing, viewing appointments, PDF generation + attach to reply
- Part E: LatentInquiryReportPreview (2-page A4 doc), ReportObjectFieldSelector
  (5 accordion groups, 35+ optional fields), mapImageUrl on Property domain

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

src/provider/IInquiryProvider.ts

@@ -10,6 +10,8 @@ export interface IInquiryProvider {
   getAll(filters?: InquiryFilters): Promise<Inquiry[]>
   getById(id: string): Promise<Inquiry | null>
   updateStatus(id: string, status: InquiryStatus): Promise<Inquiry>
+  markThreadAsRead(id: string): Promise<Inquiry>
+  getUnreadCount(): Promise<number>
   addMessage(
     inquiryId: string,
     msg: Omit<InquiryMessage, 'id' | 'inquiryId' | 'createdAt'>,