feat(dev-server): 添加开发模式 HTTP/WebSocket 服务器

功能:
- 创建 dev_server.rs 模块，提供 HTTP/WebSocket API
- 使用 feature flag \dev-server\ 控制编译
- 仅绑定 localhost:50051，安全限制 CORS
- 生产构建不包含此模块

使用方式:
- pnpm tauri:dev:web - 启动带开发服务器的 Tauri
- pnpm tauri:dev - 常规开发模式（无服务器）

安全:
- 仅 localhost 绑定
- CORS 限制为 Vite 开发端口
- 通过 feature flag 完全移除生产代码

desktop/src-tauri/src/lib.rs

@@ -29,6 +29,10 @@ mod kernel_commands;
 // Pipeline commands (DSL-based workflows)
 mod pipeline_commands;
 
+// Development server (optional, for web debugging)
+#[cfg(feature = "dev-server")]
+mod dev_server;
+
 use serde::Serialize;
 use serde_json::{json, Value};
 use std::fs;
@@ -1303,6 +1307,25 @@ fn gateway_doctor(app: AppHandle) -> Result<String, String> {
 
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
+    // Start development server when dev-server feature is enabled
+    #[cfg(feature = "dev-server")]
+    {
+        std::thread::spawn(|| {
+            let rt = tokio::runtime::Runtime::new().expect("Failed to create tokio runtime for dev server");
+            rt.block_on(async {
+                match dev_server::start_dev_server().await {
+                    Ok((_state, _handle)) => {
+                        tracing::info!("[DevServer] Development server started on port {}", dev_server::DEV_SERVER_PORT);
+                    }
+                    Err(e) => {
+                        tracing::error!("[DevServer] Failed to start: {}", e);
+                    }
+                }
+                std::future::pending::<()>().await;
+            });
+        });
+    }
+
     // Initialize Viking storage (async, in background)
     let runtime = tokio::runtime::Runtime::new().expect("Failed to create tokio runtime");
     runtime.block_on(async {