perf: 移除秒杀相关功能

packages/server/prisma/migrations/20260910030338_drop_flash_sale/migration.sql

@@ -0,0 +1,12 @@
+-- Drop flash sale feature
+-- See docs/flash-sale-removal.md for context
+--
+-- NOTE: production MySQL has no FK on orders.flash_sale_id, so we drop the
+-- column directly without a prior DROP FOREIGN KEY.
+
+-- Drop tables first
+DROP TABLE IF EXISTS `flash_sale_orders`;
+DROP TABLE IF EXISTS `flash_sales`;
+
+-- Remove order.flash_sale_id column
+ALTER TABLE `orders` DROP COLUMN `flash_sale_id`;