fix(mainsite): 修复点位管理三个bug

- 图标上传增加格式限制和提示（PNG/JPG/SVG/WebP）
- 编辑点位方法判断从 isAddMode 改为 isEditMarker，修复编辑变新增
- 删除点位 finally 中 loading 重置为 false，修复删除后UI卡死
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main/webapp/WEB-INF/views/cmpt/location.jsp

@@ -134,10 +134,12 @@
                                                     :max="1"
                                                     v-model:file-list="fileList"
                                                     list-type="image-card"
+                                                    accept=".png,.jpg,.jpeg,.svg,.webp"
                                                     @finish="uploadFinish"
                                                     >
                                                         点击上传
                                                     </n-upload>
+                                                    <span style="color:#999;font-size:12px;">支持 PNG/JPG/SVG/WebP 格式，推荐 PNG 透明背景</span>
                                                 </n-form-item>
                                                 <n-form-item label="排序" path="sortOrder">
                                                     <n-input-number   v-model:value="formData.sortOrder" placeholder="请输入排序" />
@@ -492,7 +494,7 @@
                                                         message.error(data.msg)
                                                     }
                                                 }).finally(() => {
-                                                    loading.value = true
+                                                    loading.value = false
                                                     messageReactive.destroy()
                                                     showDelModal.value = false
                                                 })

src/main/webapp/WEB-INF/views/cmpt/locationPoint.jsp

@@ -229,11 +229,12 @@
                                                     :max="1"
                                                     v-model:file-list="fileList"
                                                     list-type="image-card"
+                                                    accept=".png,.jpg,.jpeg,.svg,.webp"
                                                     @finish="uploadFinish"
                                                     >
                                                         点击上传
                                                     </n-upload>
-                                                    <span>推荐像素50x50px</span>
+                                                    <span style="color:#999;font-size:12px;">支持 PNG/JPG/SVG/WebP，推荐50x50px PNG 透明背景</span>
                                                 </n-form-item>
                                                 <n-form-item label="描述" path="description">
                                                     <n-input v-model:value="markerForm.description" placeholder="请输入描述" />
@@ -1397,7 +1398,7 @@
                                                         message.error(data.msg)
                                                     }
                                                 }).finally(() => {
-                                                    loading.value = true
+                                                    loading.value = false
                                                     messageReactive.destroy()
                                                     refreshLiveMap()
                                                 })
@@ -1424,7 +1425,7 @@
                                                     })
                                                     // 发起请求
                                                     const [err, data] = await to(fetch("/gk/location-point", {
-                                                        method: isAddMode.value ? 'POST' : 'PUT',
+                                                        method: isEditMarker.value ? 'PUT' : 'POST',
                                                         headers: {
                                                             'Content-Type': 'application/json'
                                                         },