feat: OpenRouter-ready AI service — all 11 methods implemented

IAIService:
+ generateMatchExplanation, summarizeTradeOffs, generateDataQualitySummary,
  classifyMarketSignal (4 new methods covering all documented AI output types)

OpenRouterAIService:
- All 11 methods now make real API calls via withFallback() pattern
- Every fallback is explicit (console.warn/error) — no silent mock bleed-through
- Proper JSON extraction with type-safe parsers, no any casts
- parseNeed: AI JSON → ParseNeedResult mapping (no TODO stubs)
- generateFollowUpQuestions, generateMatchExplanation, summarizeTradeOffs,
  generateDataQualitySummary, classifyMarketSignal, generateOfferEmail,
  extractCriteria, generateFollowUp: fully implemented

Prompts: +followUpQuestionsPrompt, +tradeOffPrompt, +dataQualityPrompt, +marketSignalPrompt

Factory (index.ts):
- VITE_AI_PROVIDER=mock|openrouter (new, takes priority)
- VITE_USE_REAL_AI=true still supported (legacy compat)
- Missing API key → explicit console.warn + MockAIService fallback

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

src/services/ai/IAIService.ts

@@ -49,6 +49,62 @@ export interface ParsedListingData {
   fitOut?: string
 }
 
+// ── New Response Types ────────────────────────────────────────────────────────
+
+export interface MatchExplanation {
+  headline: string
+  summary: string
+  keyReasons: string[]
+}
+
+export interface TradeOffSummary {
+  headline: string
+  items: Array<{ concern: string; severity: 'LOW' | 'MEDIUM' | 'HIGH'; mitigation?: string }>
+  overallRisk: 'LOW' | 'MEDIUM' | 'HIGH'
+}
+
+export interface DataQualitySummary {
+  overallAssessment: string
+  missingCriticalFields: string[]
+  recommendation: string
+  confidence: number
+}
+
+export interface MarketSignalClassification {
+  signalType: 'VACANCY' | 'CONSTRUCTION' | 'RESTRUCTURING' | 'EXPANSION' | 'RELOCATION' | 'UNKNOWN'
+  probability: number
+  timeHorizonMonths: number | null
+  areaSqmEstimate: number | null
+  credibility: 'LOW' | 'MEDIUM' | 'HIGH'
+  reasoning: string
+}
+
+// ── Input Types ───────────────────────────────────────────────────────────────
+
+export interface MatchExplanationInput {
+  propertyTitle: string
+  propertyCity: string
+  matchScore: number
+  positiveFactors: Array<{ criterion: string; explanation: string }>
+  negativeFactors: Array<{ criterion: string; explanation: string }>
+  needSummary: string
+}
+
+export interface TradeOffInput {
+  criterion: string
+  concern: string
+  severity: 'LOW' | 'MEDIUM' | 'HIGH'
+  mitigation?: string
+}
+
+export interface DataQualityInput {
+  score: number
+  freshness: string
+  missingCriticalFields: string[]
+  missingOptionalFields: string[]
+  warnings: string[]
+}
+
 // ── Legacy types (kept for backward compatibility) ────────────────────────────
 
 export interface CriteriaExtractionResult {
@@ -71,12 +127,22 @@ export interface IAIService {
   parseNeed(input: string): Promise<ItemResponse<ParseNeedResult>>
   generateFollowUpQuestions(criteria: ParsedNeedCriteria): Promise<ItemResponse<FollowUpQuestion[]>>
 
+  // Match explainability (F004)
+  generateMatchExplanation(input: MatchExplanationInput): Promise<ItemResponse<MatchExplanation>>
+  summarizeTradeOffs(tradeoffs: TradeOffInput[]): Promise<ItemResponse<TradeOffSummary>>
+
   // Compare (F014)
   summarizeComparison(items: UnifiedMatchResult[]): Promise<ItemResponse<ComparisonSummary>>
 
   // Shortlist decision brief
   generateDecisionBrief(shortlistId: string): Promise<ItemResponse<DecisionBrief>>
 
+  // Data quality
+  generateDataQualitySummary(propertyId: string, quality: DataQualityInput): Promise<ItemResponse<DataQualitySummary>>
+
+  // Market signal classification (OPERATIONS)
+  classifyMarketSignal(signalText: string): Promise<ItemResponse<MarketSignalClassification>>
+
   // Offer email (supply side)
   generateOfferEmail(payload: OfferEmailPayload): Promise<ItemResponse<{ subject: string; body: string }>>