fix: 全局修复所有弹窗关闭按钮显示问题

- 在全局样式中强制显示所有弹窗关闭按钮
- 对弹窗头部容器和关闭按钮强制设置显示属性
- 明确设置位置、尺寸、颜色、光标等所有属性
- 添加完整的悬浮和焦点状态样式

影响范围：全局所有使用 el-dialog 和 el-message-box 的弹窗
解决问题：新增、编辑、查看等所有类型弹窗的右上角关闭按钮不显示

web/src/assets/styles/art-element-ui.scss

@@ -805,19 +805,45 @@
   }
 }
 
+// 全局强制显示所有弹窗关闭按钮
+.el-dialog__headerbtn,
+.el-message-box__headerbtn {
+  display: block !important;
+  visibility: visible !important;
+  opacity: 1 !important;
+  position: absolute !important;
+  top: 6px !important;
+  right: 6px !important;
+  z-index: 1000 !important;
+  width: auto !important;
+  height: auto !important;
+}
+
 .el-message-box__headerbtn .el-message-box__close,
 .el-dialog__headerbtn .el-dialog__close {
+  display: block !important;
+  visibility: visible !important;
+  opacity: 1 !important;
   color: var(--art-gray-500) !important;
-  top: 7px !important;
-  right: 7px !important;
+  font-size: 16px !important;
+  width: 16px !important;
+  height: 16px !important;
   padding: 7px !important;
   border-radius: 6px !important;
   transition: all 0.3s !important;
+  background: transparent !important;
+  border: none !important;
+  cursor: pointer !important;
+  outline: none !important;
 
   &:hover {
     background-color: rgba(var(--art-gray-200-rgb), 0.7) !important;
     color: var(--art-gray-800) !important;
   }
+
+  &:focus {
+    outline: none !important;
+  }
 }
 
 .el-message-box__title {