feat(mail): 接入邮件服务并简化管理后台

- 新增 nodemailer 依赖及 SMTP 邮件发送模块
- 替换 magic link 控制台日志为真实邮件发送
- 移除仪表盘页面，管理后台默认跳转至文件管理
- 精简侧边栏导航，移除用户管理与设置入口
- 移除登录页姓名字段，品牌更名为“鼎兴”
- 关闭 biome 自动组织导入

package.json

@@ -19,6 +19,7 @@
     "drizzle-orm": "1.0.0-rc.4",
     "lucide-react": "^1.24.0",
     "next": "16.2.10",
+    "nodemailer": "^9.0.3",
     "pg": "^8.22.0",
     "proxy-agent": "^8.0.2",
     "react": "19.2.4",
@@ -32,6 +33,7 @@
     "@tailwindcss/postcss": "^4",
     "@types/ali-oss": "^6.23.3",
     "@types/node": "^20",
+    "@types/nodemailer": "^8.0.1",
     "@types/pg": "^8.20.0",
     "@types/react": "^19",
     "@types/react-dom": "^19",