feat(tradein): Phase 3.2 — /api/v1/search endpoint + Redis cache (#479)
POST /api/v1/search reading listings_search_mv with ~20 cross-source filters, parameterized SQL (CAST(:x AS type), psycopg v3), whitelisted ORDER BY (Pydantic Literal), Redis 5min hot cache with graceful degradation (singleton pool via lru_cache).
Verified vs data/sql/050_search_optimization.sql: matview column refs (total_area, lng, house_rating, sources[], has_avito/cian/yandex), SQL injection safety, cache failure swallow, router prefix.
Deep-code-reviewer: APPROVE.
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