feat: 优化微信订阅消息体系并新增约课取消通知与开课前1小时提醒

Co-authored-by: Cursor <cursoragent@cursor.com>

packages/server/prisma/migrations/20260910160000_add_class_reminder_fields/migration.sql

@@ -0,0 +1,4 @@
+-- AlterTable
+ALTER TABLE `bookings` ADD COLUMN `class_reminder_claimed_at` DATETIME(3) NULL,
+    ADD COLUMN `class_reminder_due_at` DATETIME(3) NULL,
+    ADD COLUMN `class_reminder_sent_at` DATETIME(3) NULL;