feat: gh-ost真实集成验证通过 + 登录页全面中文化 + 外观设置跨浏览器同步修复

gh-ost集成:
- handler根据instance_id查DB获取连接信息(host/port/user/password)
- 修复gh-ost参数: 去掉不存在的--dry-run(默认noop), 加--execute才真执行
- 加--skip-port-validation(端口映射环境必须)
- 加--allow-on-master(单机MySQL直接执行)
- 加--initially-drop-ghost-table/old-table/socket-file(清理残留)
- GhOstTask增加Port字段, buildArgs同步更新
- dry-run真实验证通过: 连接1.94.55.133:9005, 3行表, 3.85s完成

登录页中文化:
- 5个登录组件(SplitView/CenteredCard/SidePanel/FullImage/MinimalDark)
- 46处英文文案全部替换为中文
- 平台标题统一为'SQL审核平台'

外观设置同步修复:
- GetPublicLoginStyle: GORM First()复用主键导致第二次查询失败
- 改用Take()+重置结构体, 修复theme始终返回dark的bug
- UpdateUserPreferences: 同步写入SystemSetting表(login_style+default_theme)

frontend/src/components/login/SidePanel.tsx

@@ -29,9 +29,9 @@ export default function SidePanel() {
 
         <div style={{ position: 'relative', zIndex: 2, textAlign: 'center', maxWidth: 320 }}>
           <Database size={40} style={{ color: '#fff', marginBottom: 20 }} />
-          <h1 style={{ fontSize: 26, fontWeight: 700, color: '#fff', marginBottom: 12 }}>SQL Audit Platform</h1>
+          <h1 style={{ fontSize: 26, fontWeight: 700, color: '#fff', marginBottom: 12 }}>SQL审核平台</h1>
           <p style={{ color: 'rgba(255,255,255,0.7)', fontSize: 14, lineHeight: 1.6 }}>
-            Empowering teams with intelligent SQL auditing, real-time compliance monitoring, and actionable insights for database security.
+            为团队提供智能 SQL 审核、实时合规监控与数据库安全保障。
           </p>
         </div>
       </div>
@@ -39,21 +39,21 @@ export default function SidePanel() {
       {/* Right Panel — Login Form */}
       <div style={{ flex: 1, display: 'flex', alignItems: 'center', justifyContent: 'center', padding: 48 }}>
         <form onSubmit={handleLogin} style={{ width: '100%', maxWidth: 360, display: 'flex', flexDirection: 'column', gap: 20 }}>
-          <h2 style={{ fontSize: 22, fontWeight: 600, marginBottom: 4 }}>Welcome back</h2>
-          <p style={{ color: 'var(--dg-text-muted)', fontSize: 14, marginBottom: 8 }}>Sign in to access your dashboard</p>
+          <h2 style={{ fontSize: 22, fontWeight: 600, marginBottom: 4 }}>欢迎回来</h2>
+          <p style={{ color: 'var(--dg-text-muted)', fontSize: 14, marginBottom: 8 }}>登录以访问控制台</p>
 
           {error && <div style={{ color: '#f87171', fontSize: 13 }}>{error}</div>}
 
           <input
             type="text"
-            placeholder="Username"
+            placeholder="用户名"
             value={username}
             onChange={(e) => setUsername(e.target.value)}
             style={{ padding: '10px 14px', borderRadius: 8, background: 'var(--dg-bg-tertiary)', border: '1px solid var(--dg-border)', color: 'var(--dg-text-primary)', fontSize: 14, outline: 'none' }}
           />
           <input
             type="password"
-            placeholder="Password"
+            placeholder="密码"
             value={password}
             onChange={(e) => setPassword(e.target.value)}
             style={{ padding: '10px 14px', borderRadius: 8, background: 'var(--dg-bg-tertiary)', border: '1px solid var(--dg-border)', color: 'var(--dg-text-primary)', fontSize: 14, outline: 'none' }}
@@ -65,7 +65,7 @@ export default function SidePanel() {
             className="dg-gradient-bg"
             style={{ padding: '10px 14px', borderRadius: 8, border: 'none', color: '#fff', fontWeight: 600, fontSize: 14, cursor: loading || !username || !password ? 'not-allowed' : 'pointer', opacity: loading || !username || !password ? 0.6 : 1 }}
           >
-            {loading ? 'Signing in…' : 'Sign in'}
+            {loading ? '登录中…' : '登录'}
           </button>
         </form>
       </div>