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/mock-data/pipelineItems.ts

@@ -121,7 +121,7 @@ export const mockPipelineItems: PipelineItem[] = [
     title: 'Gewerbe Güterstrasse Basel',
     location: 'Basel',
     matchScore: 68,
-    resultType: 'EXTERNAL_MARKET',
+    resultType: 'VERIFIED_PORTFOLIO',
     stage: 'CLOSED_LOST',
     areaLabel: '800 m²',
     rentLabel: 'CHF 28/m²',