fix: DialogContent 添加默认 padding p-6，修复确认弹框布局压缩问题

- dialog.tsx: DialogContent 基础样式加 p-6 (24px padding)
- ConfirmDialog.tsx: 按钮区域间距 pt-2 → pt-4
- 修复所有使用 Radix Dialog 的弹框内容紧贴边缘的问题

frontend/src/components/ui/dialog.tsx

@@ -54,7 +54,7 @@ function DialogContent({
           "data-[state=closed]:zoom-out-95 data-[state=open]:zoom-in-95",
           "fixed z-[101] top-[50%] left-[50%] -translate-x-1/2 -translate-y-1/2",
           "w-full max-w-[calc(100%-2rem)] sm:max-w-lg",
-          "rounded-xl shadow-2xl",
+          "rounded-xl shadow-2xl p-6",
           "max-h-[85vh] flex flex-col",
           "outline-none duration-200",
           className