feat: Marktchancen — Netzwerk-Hinweise tab (human-sourced market intel)

- MarktHinweis domain type: SUCHE/VERFUEGBARKEIT direction, INTERN/PLATTFORM
  visibility, anonymization flag, source tracking
- Full data layer: IMarktHinweisProvider, MockupMarktHinweisProvider, service, hooks
- 7 seed entries: mix of intern/shared, demand/supply, own/partner Verwaltungen
- Marktchancen gets two-tab layout: Digitale Signale (crawler) + Netzwerk (human)
- HinweisListItem: direction icon, visibility badge (Intern/Geteilt/partner name)
- HinweisDetail: note card, portfolio match (SUCHE) or availability info (VERFUEGBARKEIT)
- HinweisErfassenDialog: direction toggle, asset type, location, area range,
  company + anonymize switch, source, note, card-based visibility picker
- HinweisPropertyCard: same Anschreiben composer pattern as crawler side

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

src/services/marktHinweisService.ts

@@ -0,0 +1,11 @@
+import { MockupMarktHinweisProvider } from '../provider/MockupMarktHinweisProvider'
+import type { MarktHinweis, CreateMarktHinweisInput } from '../domain/marktHinweis'
+
+const provider = MockupMarktHinweisProvider
+
+export const marktHinweisService = {
+  getAll: (): Promise<MarktHinweis[]> => provider.getAll(),
+  getById: (id: string): Promise<MarktHinweis | null> => provider.getById(id),
+  create: (data: CreateMarktHinweisInput): Promise<MarktHinweis> => provider.create(data),
+  update: (id: string, data: Partial<MarktHinweis>): Promise<MarktHinweis> => provider.update(id, data),
+}