feat(channel): add mci-channel-wechat-personal adapter

- New module: mci-channel-wechat-personal
- Implements ChannelAdapter SPI for personal WeChat
- Calls Python channel-service pywechat HTTP APIs:
  - /v1/wechat-personal/login/start for initAccount QR code
  - /v1/wechat-personal/send/text and /send/image for sendMessage
- Configurable base URL via sino.channel.wechat-personal.base-url
- Added MockWebServer unit tests
- Wired module into backend parent and mci-server

backend/pom.xml

@@ -30,6 +30,7 @@
         <module>mci-shared</module>
         <module>mci-channel-common</module>
         <module>mci-channel-wecom</module>
+        <module>mci-channel-wechat-personal</module>
         <module>mci-server</module>
     </modules>
 
@@ -50,6 +51,11 @@
                 <artifactId>mci-channel-wecom</artifactId>
                 <version>${project.version}</version>
             </dependency>
+            <dependency>
+                <groupId>com.sino</groupId>
+                <artifactId>mci-channel-wechat-personal</artifactId>
+                <version>${project.version}</version>
+            </dependency>
             <dependency>
                 <groupId>com.baomidou</groupId>
                 <artifactId>mybatis-plus-boot-starter</artifactId>