feat: remove EXTERNAL_MARKET result type entirely

All external market properties now surface as VERIFIED_PORTFOLIO.
Removes the type from enums, domain types, mock data, matching engine,
components, hooks, and tests — zero user-visible distinction remains.

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

src/domain/unifiedResult.ts

@@ -15,14 +15,7 @@ interface UnifiedResultBase {
 }
 
 export interface VerifiedPortfolioResult extends UnifiedResultBase {
-  resultType: 'VERIFIED_PORTFOLIO'
-  property: Property
-  match: Match
-  unit?: PropertyUnit    // specific unit this match refers to
-}
-
-export interface ExternalMarketResult extends UnifiedResultBase {
-  resultType: 'EXTERNAL_MARKET' | 'MAISON_WORK'
+  resultType: 'VERIFIED_PORTFOLIO' | 'MAISON_WORK'
   property: Property
   match: Match
   unit?: PropertyUnit    // specific unit this match refers to
@@ -38,5 +31,4 @@ export interface FutureAvailabilityResult extends UnifiedResultBase {
 
 export type UnifiedMatchResult =
   | VerifiedPortfolioResult
-  | ExternalMarketResult
   | FutureAvailabilityResult