🐛 fix(server): 修复数据库初始化时的潜在空指针异常

- 添加AppDataSource存在性检查，防止在未定义时访问isInitialized属性
- 增强数据库初始化逻辑的健壮性，避免应用启动失败

packages/server/src/index.ts

@@ -11,7 +11,7 @@ import { databaseBackup } from './utils/backup'
 import { UserEntity, Role } from '@d8d/user-module'
 import { File } from '@d8d/file-module'
 
-if(!AppDataSource.isInitialized) {
+if(!AppDataSource || !AppDataSource.isInitialized) {
   initializeDataSource([UserEntity, Role, File])
   await AppDataSource.initialize();
   console.log('数据库初始化完成')