feat(proto): 添加设备通信协议v1修订版及统一帧格式

- 新增docs/device_communication_protocol_v1.md文档，定义V1修订版协议
- CDC和BLE GATT均改为直接传输业务消息，去掉外层协议封装
- BLE改为使用NUS(Nordic UART Service)替代原有GATT服务
- 统一键盘位图为29字节格式，FunctionKeyEvent改为上报全键盘位图
- 顶层消息增加msg_id和reply_to字段用于请求响应匹配
- Ack和Error合并为统一Response消息类型
- CDC和NUS均增加统一外层帧格式：magic(2) + len(1) + protobuf
- 添加Proto frame常量定义及长度验证逻辑
- 更新proto文件定义，包含DeviceMessage统一信封和ResponseCode枚举

- 重构hid_flowctrl_module.c中的上下文访问方式，统一使用ctx前缀

proto/device_comm.proto

@@ -1,5 +1,13 @@
 syntax = "proto3";
 
+enum ResponseCode {
+  RESPONSE_CODE_OK = 0;
+  RESPONSE_CODE_UNKNOWN_TYPE = 1;
+  RESPONSE_CODE_INVALID_LENGTH = 2;
+  RESPONSE_CODE_INVALID_PARAM = 3;
+  RESPONSE_CODE_NOT_READY = 4;
+}
+
 message HelloReq {
   uint32 protocol_version = 1;
 }
@@ -39,24 +47,14 @@ message ThemeRgb {
   uint32 blue = 3;
 }
 
-message Ack {
-  uint32 acked_type = 1;
+message Response {
+  ResponseCode error_code = 1;
 }
 
-enum ErrorCode {
-  ERROR_CODE_NONE = 0;
-  ERROR_CODE_UNKNOWN_TYPE = 1;
-  ERROR_CODE_INVALID_LENGTH = 2;
-  ERROR_CODE_INVALID_PARAM = 3;
-  ERROR_CODE_NOT_READY = 4;
-}
+message DeviceMessage {
+  uint32 msg_id = 10;
+  uint32 reply_to = 11;
 
-message Error {
-  uint32 error_type = 1;
-  ErrorCode error_code = 2;
-}
-
-message CdcPacketBody {
   oneof body {
     HelloReq hello_req = 1;
     HelloRsp hello_rsp = 2;
@@ -65,7 +63,6 @@ message CdcPacketBody {
     LedState led_state = 5;
     TimeSync time_sync = 6;
     ThemeRgb theme_rgb = 7;
-    Ack ack = 8;
-    Error error = 9;
+    Response response = 8;
   }
 }