fix: 可用性监控仅统计终态请求

drizzle/0088_amazing_energizer.sql

@@ -0,0 +1,4 @@
+-- Note: message_request is a high-write table. Standard CREATE INDEX may block writes during index creation.
+-- Drizzle migrator does not support CREATE INDEX CONCURRENTLY. If write blocking is a concern,
+-- manually pre-create this index with CONCURRENTLY before running this migration (IF NOT EXISTS prevents conflicts).
+CREATE INDEX IF NOT EXISTS "idx_message_request_provider_created_at_finalized_active" ON "message_request" USING btree ("provider_id","created_at" DESC NULLS LAST) WHERE "message_request"."deleted_at" IS NULL AND "message_request"."status_code" IS NOT NULL;