feat: 品牌重命名 SQL-Platform → OpsxSQL — 12个文件18处替换，覆盖所有登录组件+Layout+index.html

frontend/index.html

@@ -4,7 +4,7 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <link rel="icon" type="image/svg+xml" href="/favicon.svg" />
-    <title>SQL-Platform</title>
+    <title>OpsxSQL</title>
   </head>
   <body>
     <div id="root"></div>