feat: Marktsignale KPI panel with adjustable radius (5/10/15/20 km)

Adds MarketKpis domain type with formula-based radius scaling, a MarketKpiPanel
component (vacancy rate, platform searches, avg vacancy duration, demand/supply
ratio — color-coded with interpretation badges), and integrates it at the top of
PropertyMarketSignalsTab. Demand/supply section labels now update with the
selected radius. Mock data covers all 5 existing market reports.

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

src/domain/marketReport.ts

@@ -11,8 +11,32 @@ export interface PropertyMarketSignal {
   confidence?: number
 }
 
+// Key market performance indicators for a given radius.
+// Base values are stored at 5 km; other radii are computed via getKpisForRadius().
+export interface MarketKpis {
+  vacancyRatePct: number        // % of comparable properties currently vacant
+  activePlatformSearches: number // active search requests on the platform
+  avgVacancyMonths: number      // average months comparable properties remain vacant
+  demandSupplyRatio: number     // demand / supply ratio (> 1 = more demand than supply)
+  comparableListings: number    // number of comparable active listings
+}
+
+/** Scale base KPIs (at 5 km) for a larger radius. */
+export function getKpisForRadius(base: MarketKpis, radiusKm: number): MarketKpis {
+  const f = radiusKm / 5
+  return {
+    vacancyRatePct:           +Math.min(35, base.vacancyRatePct + (f - 1) * 1.8).toFixed(1),
+    activePlatformSearches:   Math.round(base.activePlatformSearches * f * 0.85),
+    avgVacancyMonths:         +Math.min(24, base.avgVacancyMonths * (1 + (f - 1) * 0.12)).toFixed(1),
+    demandSupplyRatio:        +Math.max(0.3, base.demandSupplyRatio / (1 + (f - 1) * 0.18)).toFixed(1),
+    comparableListings:       Math.round(base.comparableListings * f * 1.1),
+  }
+}
+
 export interface MarketReport {
   propertyId: string
   generatedAt: string
+  assetTypeLabel: string   // e.g. "Büro"
+  kpis: MarketKpis         // base values at 5 km radius
   signals: PropertyMarketSignal[]
 }