chore: 为 OAuth 回调链路添加墙钟时间日志

定位 19s 延迟：Rust 命令本体 0ms 完成，延迟在 Tauri IPC 往返。
前后端各步骤加 wall= 时间戳，便于比对 invoke 投递 vs 结果返回耗时。

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

src-tauri/src/commands/oauth_server.rs

@@ -40,9 +40,10 @@ pub async fn oauth_start_callback_server(
     let t0 = std::time::Instant::now();
     let log = |step: &str| {
         println!(
-            "[OAuth Callback] {} +{}ms",
+            "[OAuth Callback] {} +{}ms (wall={})",
             step,
-            t0.elapsed().as_millis()
+            t0.elapsed().as_millis(),
+            chrono::Local::now().format("%H:%M:%S%.3f")
         );
     };
     log("oauth_start_callback_server enter");

src/components/OAuth/OAuthLogin.tsx

@@ -129,7 +129,9 @@ export function OAuthLogin({ visible, onClose, onSuccess }: OAuthLoginProps) {
     setLoading(true)
     const t0 = performance.now()
     const log = (step: string) =>
-      console.log(`[OAuthLogin] ${step} +${Math.round(performance.now() - t0)}ms`)
+      console.log(
+        `[OAuthLogin] ${step} +${Math.round(performance.now() - t0)}ms (wall=${new Date().toISOString()})`
+      )
     log("handleOAuthLogin start")
 
     try {