修复(#85): 补充促销迁移幂等处理

Co-authored-by: multica-agent <github@multica.ai>

initialize/migrate/database/02154_promo_system.up.sql

@@ -99,6 +99,16 @@ PREPARE stmt FROM @sql;
 EXECUTE stmt;
 DEALLOCATE PREPARE stmt;
 
+SET @sql = IF(
+  @column_exists = 1,
+  'ALTER TABLE `subscribe_promo` MODIFY COLUMN `quantity` BIGINT NOT NULL DEFAULT 1 COMMENT ''购买数量''',
+  'SELECT ''Column quantity does not exist in subscribe_promo table'''
+);
+
+PREPARE stmt FROM @sql;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+
 SET @index_exists = (
   SELECT COUNT(*)
   FROM INFORMATION_SCHEMA.STATISTICS
@@ -117,6 +127,24 @@ PREPARE stmt FROM @sql;
 EXECUTE stmt;
 DEALLOCATE PREPARE stmt;
 
+SET @index_exists = (
+  SELECT COUNT(*)
+  FROM INFORMATION_SCHEMA.STATISTICS
+  WHERE TABLE_SCHEMA = DATABASE()
+    AND TABLE_NAME = 'subscribe_promo'
+    AND INDEX_NAME = 'uk_subscribe_qty_rule'
+);
+
+SET @sql = IF(
+  @index_exists = 1,
+  'ALTER TABLE `subscribe_promo` DROP INDEX `uk_subscribe_qty_rule`',
+  'SELECT ''Index uk_subscribe_qty_rule does not exist on subscribe_promo table'''
+);
+
+PREPARE stmt FROM @sql;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+
 SET @index_exists = (
   SELECT COUNT(*)
   FROM INFORMATION_SCHEMA.STATISTICS