🎨 优化管理员系统设置页面布局

在"最大上传大小"设置旁边添加保存按钮，使其更明显
添加提示：修改后需要重启服务才能生效

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/app.html

@@ -1635,11 +1635,15 @@
         <h3 style="margin-bottom: 20px;">
           <i class="fas fa-sliders-h"></i> 系统设置
         </h3>
-        <div style="display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 16px;">
-          <div class="form-group">
+        <div style="display: flex; align-items: flex-end; gap: 16px; flex-wrap: wrap;">
+          <div class="form-group" style="margin-bottom: 0;">
             <label class="form-label">最大上传大小 (MB)</label>
-            <input type="number" class="form-input" v-model.number="systemSettings.maxUploadSizeMB" min="1">
+            <input type="number" class="form-input" v-model.number="systemSettings.maxUploadSizeMB" min="1" style="width: 150px;">
           </div>
+          <button class="btn btn-primary" @click="updateSystemSettings" style="height: 40px;">
+            <i class="fas fa-save"></i> 保存
+          </button>
+          <span style="color: #666; font-size: 13px;">修改后需要重启服务才能生效</span>
         </div>
         <hr style="margin: 20px 0;">
         <h4 style="margin-bottom: 12px;">SMTP 邮件配置（用于注册激活和找回密码）</h4>