refactor(backend): 更新数据库配置并迁移至MySQL，优化文档和技术栈描述

backend/src/config/database.js

@@ -1,22 +1,21 @@
 const mysql = require('mysql2/promise');
+const config = require('./env');
 
 // 数据库配置
 const dbConfig = {
   host: process.env.DB_HOST || '129.211.213.226',
   port: process.env.DB_PORT || 9527,
   user: process.env.DB_USER || 'root',
-  password: process.env.DB_PASSWORD || 'aiotAiot123!',
+  password: process.env.DB_PASSWORD || 'Aiot123',
   database: process.env.DB_NAME || 'jiebandata',
-  connectionLimit: 10,
-  charset: 'utf8mb4',
-  timezone: '+08:00',
+  connectionLimit: process.env.DB_CONNECTION_LIMIT || 10,
+  charset: process.env.DB_CHARSET || 'utf8mb4',
+  timezone: process.env.DB_TIMEZONE || '+08:00',
   // 连接池配置
   waitForConnections: true,
   queueLimit: 0,
   // 超时配置
-  connectTimeout: 10000, // 10秒连接超时
-  acquireTimeout: 10000, // 10秒获取连接超时
-  timeout: 10000 // 10秒查询超时
+  connectTimeout: 10000 // 10秒连接超时
 };
 
 // 创建连接池