feat(M04-A): 完成定价快照与并发时段预占

database/migrations/2026061811_m04a_pricing_reservations.down.sql

@@ -0,0 +1,8 @@
+DELETE FROM qipai_schema_migrations WHERE version = '2026061811';
+DROP TABLE IF EXISTS qipai_room_reservations;
+DROP TABLE IF EXISTS qipai_order_price_snapshots;
+DROP TABLE IF EXISTS qipai_holiday_calendar;
+ALTER TABLE qipai_orders DROP COLUMN hold_expires_at;
+ALTER TABLE qipai_rooms
+  DROP COLUMN minimum_spend_cents,
+  DROP COLUMN full_day_price_cents;