新增大厅订单容量控制

apps/backend/src/db/migrations/051_worker_hall_queue.sql

@@ -0,0 +1,14 @@
+-- 051_worker_hall_queue.sql —— 抢单大厅展示队列与容量查询索引。
+
+ALTER TABLE work_orders ADD COLUMN IF NOT EXISTS hall_queued_at TIMESTAMPTZ NULL;
+
+UPDATE work_orders
+SET hall_queued_at = COALESCE(published_at, updated_at, created_at)
+WHERE status = 'open'
+  AND hall_queued_at IS NULL;
+
+CREATE INDEX IF NOT EXISTS idx_work_orders_hall_queue
+  ON work_orders(hall_queued_at ASC, id ASC)
+  WHERE status = 'open';
+
+COMMENT ON COLUMN work_orders.hall_queued_at IS '进入抢单大厅候选队列的时间；用于按先进先出限制大厅展示数量';