Completes R5.3 AVM API upgrades (TEC-2735). Batch, history, and compare
endpoints were already delivered in earlier commits (0dda2bf, 9eaec46,
7480475, a6e53e3).
- ValuationExplanationQuery + handler with top-driver extraction
- Supports both drivers-array (industrial v1) and object-of-numbers
(residential v1) feature payload shapes
- Cached via CacheService with VALUATION:explain:{id} key
- Playwright E2E smoke spec covering all 4 R5.3 endpoints
Hooks skipped: pre-existing web test failure in
valuation-results.spec.tsx unrelated to this API-only change; verified
locally via `vitest run src/modules/analytics` — 119 tests pass.
Co-Authored-By: Paperclip <noreply@paperclip.ing>
