feat: 添加 RustDesk 协议支持和项目文档

- 新增 RustDesk 模块，支持与 RustDesk 客户端连接
  - 实现会合服务器协议和 P2P 连接
  - 支持 NaCl 加密和密钥交换
  - 添加视频帧和 HID 事件适配器
- 添加 Protobuf 协议定义 (message.proto, rendezvous.proto)
- 新增完整项目文档
  - 各功能模块文档 (video, hid, msd, otg, webrtc 等)
  - hwcodec 和 RustDesk 协议技术报告
  - 系统架构和技术栈文档
- 更新 Web 前端 RustDesk 配置界面和 API

src/webrtc/webrtc_streamer.rs

@@ -293,6 +293,26 @@ impl WebRtcStreamer {
         Ok(pipeline)
     }
 
+    /// Ensure video pipeline is running and return it for external consumers
+    ///
+    /// This is a public wrapper around ensure_video_pipeline for external
+    /// components (like RustDesk) that need to share the encoded video stream.
+    pub async fn ensure_video_pipeline_for_external(
+        &self,
+        tx: broadcast::Sender<VideoFrame>,
+    ) -> Result<Arc<SharedVideoPipeline>> {
+        self.ensure_video_pipeline(tx).await
+    }
+
+    /// Get the current pipeline configuration (if pipeline is running)
+    pub async fn get_pipeline_config(&self) -> Option<SharedVideoPipelineConfig> {
+        if let Some(ref pipeline) = *self.video_pipeline.read().await {
+            Some(pipeline.config().await)
+        } else {
+            None
+        }
+    }
+
     // === Audio Management ===
 
     /// Check if audio is enabled