search: cache results

server/prisma/migrations/20260531000000_add_search_query_cache_key/migration.sql

@@ -0,0 +1,8 @@
+-- Add normalized search query lookup key for cache/reuse behavior.
+ALTER TABLE "Search" ADD COLUMN "queryNormalized" TEXT;
+
+UPDATE "Search"
+SET "queryNormalized" = lower(trim("query"))
+WHERE "query" IS NOT NULL AND trim("query") != '';
+
+CREATE INDEX "Search_queryNormalized_updatedAt_idx" ON "Search"("queryNormalized", "updatedAt");