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/scoring.ts

@@ -42,7 +42,6 @@ export const DATA_QUALITY_MODIFIER = {
 export const CONFIDENCE_MODIFIER = {
   VERIFIED_HIGH:       +3,  // VERIFIED_PORTFOLIO + confidenceScore >= 0.80
   VERIFIED_MEDIUM:      0,  // VERIFIED_PORTFOLIO + confidenceScore < 0.80
-  EXTERNAL_MARKET:     -3,  // EXTERNAL_MARKET result type
   MAISON_WORK:         -2,  // MAISON_WORK — Maison Work API (slightly more trusted than scraped market)
   FUTURE_AVAILABILITY: -15, // FUTURE_AVAILABILITY — never treat as confirmed availability
   LOW_CONFIDENCE:      -10, // confidenceScore < 0.50 (stacks with above)