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)

backend/internal/ghost/ghost.go

@@ -13,6 +13,7 @@ import (
 // GhOstTask defines a gh-ost execution task
 type GhOstTask struct {
 	Host           string `json:"host"`
+	Port           int    `json:"port,omitempty"`
 	User           string `json:"user"`
 	Password       string `json:"password"`
 	Database       string `json:"database"`
@@ -60,12 +61,18 @@ func RunGhOst(ctx context.Context, task GhOstTask, ghOstPath string) (*GhOstResu
 
 	args := []string{
 		"--host=" + task.Host,
+		fmt.Sprintf("--port=%d", task.Port),
 		"--user=" + task.User,
 		"--password=" + task.Password,
 		"--database=" + task.Database,
 		"--table=" + task.Table,
 		"--alter=" + task.Alter,
 		"--verbose",
+		"--skip-port-validation",
+		"--allow-on-master",
+		"--initially-drop-ghost-table",
+		"--initially-drop-old-table",
+		"--initially-drop-socket-file",
 	}
 
 	if task.ChunkSize > 0 {
@@ -91,11 +98,11 @@ func RunGhOst(ctx context.Context, task GhOstTask, ghOstPath string) (*GhOstResu
 	}
 
 	// Dry-Run vs Execute
-	if task.DryRun || !task.Execute {
-		args = append(args, "--dry-run")
-	} else {
+	// gh-ost defaults to noop (dry-run), only --execute actually applies changes
+	if task.Execute {
 		args = append(args, "--execute")
 	}
+	// always verbose for output
 
 	cmd := exec.CommandContext(ctx, ghOstPath, args...)
 	var stdout, stderr bytes.Buffer
@@ -193,12 +200,18 @@ func (m *TaskManager) ListTasks() map[string]string {
 func buildArgs(task GhOstTask, ghOstPath string) []string {
 	args := []string{
 		"--host=" + task.Host,
+		fmt.Sprintf("--port=%d", task.Port),
 		"--user=" + task.User,
 		"--password=" + task.Password,
 		"--database=" + task.Database,
 		"--table=" + task.Table,
 		"--alter=" + task.Alter,
 		"--verbose",
+		"--skip-port-validation",
+		"--allow-on-master",
+		"--initially-drop-ghost-table",
+		"--initially-drop-old-table",
+		"--initially-drop-socket-file",
 	}
 
 	if task.ChunkSize > 0 {
@@ -223,9 +236,8 @@ func buildArgs(task GhOstTask, ghOstPath string) []string {
 		args = append(args, "--postpone-cut-over-flag-file=/tmp/gh-ost-cutover.flag")
 	}
 
-	if task.DryRun || !task.Execute {
-		args = append(args, "--dry-run")
-	} else {
+	// gh-ost defaults to noop, only --execute actually applies changes
+	if task.Execute {
 		args = append(args, "--execute")
 	}