fix: use tauri::async_runtime::spawn for MCP server

tokio::spawn panics in .setup() because Tauri's Tokio reactor isn't
active yet at that point. tauri::async_runtime::spawn handles this.

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

src-tauri/src/lib.rs

@@ -24,7 +24,7 @@ pub fn run() {
                 .expect("failed to resolve app data dir")
                 .join("connections.json");
 
-            tokio::spawn(async move {
+            tauri::async_runtime::spawn(async move {
                 if let Err(e) = mcp::start_mcp_server(state, connections_path, 9427).await {
                     log::error!("MCP server error: {}", e);
                 }