change(dms):修复设备图片字段清空逻辑并优化卡片布局

- 将图片字段清空方式从 undefined 改为显式设置为空字符串，确保后端正确更新
- 设备卡片容器增加 align-items: stretch 以保持一致高度
- 调整 .machine-card 样式以支持弹性布局，预留底部操作区域空间
- 快捷操作按钮组定位到底部，并横向居中显示- 统一卡片内边距，增强视觉一致性

src/views/dms/prodBaseMachineInfo/index.vue

@@ -1117,8 +1117,9 @@ const submitForm = () => {
           form.value.ossId = form.value.file[0].ossId;
           form.value.photoAddress = form.value.file[0].url;
         } else {
-          form.value.ossId = undefined;
-          form.value.photoAddress = undefined;
+          // 显式清空图片字段，确保后端更新
+          form.value.ossId = '';
+          form.value.photoAddress = '';
         }
 
         if (form.value.machineId) {
@@ -1741,18 +1742,25 @@ watch(selectedMachine, (newMachine) => {
       grid-template-columns: repeat(5, 1fr); // 修改为一行5个
       gap: 8px;
       margin-bottom: 16px;
+      align-items: stretch;
     }
 
     .machine-card-wrapper {
       cursor: pointer;
+      height: 100%;
 
       .machine-card {
         background: #fff;
         border-radius: 4px;
-        padding: 8px;
+        padding: 8px 8px 44px; // 预留底部操作区空间
         box-shadow: 0 1px 4px rgba(0, 0, 0, 0.1);
         transition: all 0.3s ease;
         position: relative;
+        height: 160px;
+        display: flex;
+        flex-direction: column;
+        justify-content: space-between;
+        box-sizing: border-box;
 
         &:hover {
           transform: translateY(-1px);
@@ -1852,6 +1860,10 @@ watch(selectedMachine, (newMachine) => {
         }
 
         .quick-actions {
+          position: absolute;
+          left: 8px;
+          right: 8px;
+          bottom: 8px;
           display: flex;
           gap: 4px;
           justify-content: center;