feat(msg): 修复通知服务并添加ES降级与Push Gateway推送

database.ts 导出db常量替代getDb()函数

env.ts JWT_SECRET/ES_URL改optional加DEV_MODE/PUSH_GATEWAY_URL

elasticsearch.ts ES降级: ES_URL未设置时esClient=null

notifications.service.ts 加createBatch+分页查询+Push Gateway推送调用

新建msg-init.sql创建2张表

scripts/msg-init.sql

@@ -0,0 +1,26 @@
+-- Msg 服务数据库初始化脚本
+-- 表：msg_notifications / msg_notification_preferences
+
+CREATE TABLE IF NOT EXISTS msg_notifications (
+  id CHAR(36) NOT NULL PRIMARY KEY,
+  user_id CHAR(36) NOT NULL,
+  type VARCHAR(50) NOT NULL,
+  title VARCHAR(200) NOT NULL,
+  content TEXT NOT NULL,
+  channel VARCHAR(20) NOT NULL DEFAULT 'in_app',
+  is_read BOOLEAN NOT NULL DEFAULT FALSE,
+  metadata JSON NULL,
+  created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  INDEX idx_notifications_user_id (user_id),
+  INDEX idx_notifications_is_read (is_read),
+  INDEX idx_notifications_created_at (created_at),
+  INDEX idx_notifications_user_read (user_id, is_read)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
+
+CREATE TABLE IF NOT EXISTS msg_notification_preferences (
+  user_id CHAR(36) NOT NULL PRIMARY KEY,
+  email_enabled BOOLEAN NOT NULL DEFAULT TRUE,
+  sms_enabled BOOLEAN NOT NULL DEFAULT FALSE,
+  push_enabled BOOLEAN NOT NULL DEFAULT TRUE,
+  in_app_enabled BOOLEAN NOT NULL DEFAULT TRUE
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;