feat: F021 market intelligence & signal discovery

Signal domain types, mock data (8 signals), provider interface + MockupMarketIntelligenceProvider, marketIntelligenceService, TanStack Query hooks, 10 ops components (SignalInbox, MarketSignalCard, MarketSignalFilterBar, MarketSignalSkeleton, MarketSignalEmptyState, SignalConfidenceBadge, SourceReliabilityBadge, SensitivityWarningPanel, SignalConversionPanel, SignalEvidenceList), MarketIntelligence page wired into AppShell nav and App router.

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

src/provider/IMarketIntelligenceProvider.ts

@@ -0,0 +1,13 @@
+import type { MarketSignal, MarketSignalFilters, SignalProcessingStatus } from '../domain/marketSignal'
+
+export interface IMarketIntelligenceProvider {
+  getSignals(filters?: MarketSignalFilters): Promise<MarketSignal[]>
+  getSignalById(id: string): Promise<MarketSignal | null>
+  updateSignalStatus(id: string, status: SignalProcessingStatus): Promise<MarketSignal>
+  convertToFutureSignal(id: string): Promise<{ futureSignalId: string }>
+  linkSignalToEntity(
+    id: string,
+    entityType: 'property' | 'need',
+    entityId: string,
+  ): Promise<MarketSignal>
+}