✨ feat(mqtt): 新增 MQTT 数据源连接与测试发消息支持

frontend/src/components/MessagePublishModal.tsx

@@ -1,5 +1,5 @@
 import React, { useEffect, useMemo, useState } from 'react';
-import { Alert, Form, Input, Modal, Select, Space, Typography, message } from 'antd';
+import { Alert, Checkbox, Form, Input, Modal, Select, Space, Typography, message } from 'antd';
 
 import { DBQuery } from '../../wailsjs/go/app/App';
 import type { SavedConnection } from '../types';
@@ -149,6 +149,28 @@ const MessagePublishModal: React.FC<MessagePublishModalProps> = ({
             </Form.Item>
           )}
 
+          {presentation.showQos && (
+            <Form.Item
+              label="QoS"
+              name="qos"
+              extra="0 为至多一次，1 为至少一次，2 为仅一次。"
+            >
+              <Select
+                options={[
+                  { label: '0 · At most once', value: 0 },
+                  { label: '1 · At least once', value: 1 },
+                  { label: '2 · Exactly once', value: 2 },
+                ]}
+              />
+            </Form.Item>
+          )}
+
+          {presentation.showRetain && (
+            <Form.Item name="retain" valuePropName="checked" style={{ marginBottom: 16 }}>
+              <Checkbox>Retain 消息</Checkbox>
+            </Form.Item>
+          )}
+
           {presentation.showKey && (
             <Form.Item label="消息 Key（可选）">
               <Space.Compact style={{ width: '100%' }}>