feat(streamProxy): Mapper新增selectByCameraCode查询方法

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main/java/com/genersoft/iot/vmp/streamProxy/dao/StreamProxyMapper.java

@@ -92,4 +92,12 @@ public interface StreamProxyMapper {
             " stream_key = #{streamKey} " +
             " WHERE id=#{id}")
     void updateStream(StreamProxy streamProxy);
+
+    /**
+     * 根据 camera_code 查询拉流代理
+     * @param cameraCode 摄像头全局唯一编码
+     * @return StreamProxy 对象，不存在返回 null
+     */
+    @Select("SELECT * FROM wvp_stream_proxy WHERE camera_code = #{cameraCode}")
+    StreamProxy selectByCameraCode(@Param("cameraCode") String cameraCode);
 }