feat: Marktchancen — source links, KI-Kontaktdaten, portfolio match, Anschreiben

- ExtractedContact domain type (ContactType, ContactConfidence) on FutureSignal
- Mock extractedContacts for all 6 DEMAND signals (website, email, phone/linkedin)
- Source URL row with external link button
- KI-Kontaktdaten section: clickable links, confidence dots, purple accent
- PropertyMatchCard: area fit % chip (green/yellow/red), inline Anschreiben toggle
- buildAnschreiben() pre-filled German outreach template, editable + copy button
- Portfolio match section groups properties by fit quality

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

src/domain/futureSignal.ts

@@ -1,5 +1,15 @@
 import type { SignalType, RiskLevel, ReviewStatus } from './enums'
 
+export type ContactType = 'EMAIL' | 'PHONE' | 'WEBSITE' | 'LINKEDIN' | 'CONTACT_PERSON'
+export type ContactConfidence = 'HIGH' | 'MEDIUM' | 'LOW'
+
+export interface ExtractedContact {
+  type: ContactType
+  value: string
+  confidence: ContactConfidence
+  label?: string
+}
+
 export interface SignalSource {
   type: 'PRESS' | 'CONSTRUCTION_PERMIT' | 'JOB_POSTING' | 'COMPANY_REPORT' | 'MARKET_DATA' | 'MANUAL' | 'LEASE_CONTRACT'
   url?: string
@@ -58,4 +68,7 @@ export interface FutureSignal {
 
   // Unit-level reference: if set, this signal is about a specific rentable unit
   unitId?: string
+
+  // KI-extracted contact information from web crawler sources
+  extractedContacts?: ExtractedContact[]
 }