fix(admin): bind FaIconPicker with v-model so icon clicks update the value

assets/admin/src/pages/content/FooterTabbarSettings.vue

@@ -129,7 +129,7 @@
         </n-form-item>
 
         <n-form-item label="图标 (Font Awesome / 内置 SVG)">
-          <FaIconPicker v-model:value="editingItem.icon" placeholder="选择图标" />
+          <FaIconPicker v-model="editingItem.icon" placeholder="选择图标" />
           <template #feedback>
             <div class="icon-preview-row">
               <span>预览：</span>
@@ -227,7 +227,7 @@
                     <i class="fa fas fa-bars"></i>
                   </button>
                   <n-input v-model:value="element.label" placeholder="名称，例如：写文章" />
-                  <FaIconPicker v-model:value="element.icon" placeholder="选择图标" />
+                  <FaIconPicker v-model="element.icon" placeholder="选择图标" />
                   <n-input v-model:value="element.url" placeholder="链接，例如：/wp-admin/post-new.php" />
                   <n-button quaternary type="error" @click="removeAddItem(subIndex)">
                     <template #icon><i class="fa fas fa-trash-alt" /></template>