fix: use hostname:8000 as API fallback for remote deployments

Replace hardcoded localhost:8000 with window.location.hostname:8000 so the
frontend auto-detects the correct backend address when deployed on a remote
server instead of always pointing to localhost.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/src/lib/api.ts

@@ -12,7 +12,7 @@ import type {
 } from "@/types";
 
 // API基础配置
-const API_BASE_URL = process.env.NEXT_PUBLIC_API_URL || (typeof window !== 'undefined' ? `${window.location.protocol}//${window.location.host}/api` : "http://127.0.0.1:8000");
+const API_BASE_URL = process.env.NEXT_PUBLIC_API_URL || (typeof window !== 'undefined' ? `${window.location.protocol}//${window.location.hostname}:8000` : "http://127.0.0.1:8000");
 
 // 请求拦截器
 async function apiRequest<T>(