Sub-directory deploy breaks routes, icons and API calls

• GET https://example.cn/icons/poi.png 404 and GET https://example.cn/api/layers 404 while the app lives at /gis/.
• import.meta.env.BASE_URL prints '/' because base was never configured.
• location.pathname is /gis/index.html but router links point at /map.

1. Inspect the built index.html for asset URLs starting with /gis/.
2. Read location.pathname to confirm the real deployment prefix.
3. Search the code for fetch, image and tile paths beginning with a slash.
4. Check the router history base and the Nginx location block.

Set base: '/gis/' (or process.env.DEPLOY_BASE) in vite.config, create the router with createWebHistory(import.meta.env.BASE_URL), build URLs from import.meta.env.BASE_URL, and configure Nginx with alias /var/www/gis/dist/ plus try_files fallback to /gis/index.html.

GET https://example.cn/icons/poi.png 404 (Not Found)
GET https://example.cn/api/layers 404 (Not Found)
# 实际部署位置是 https://example.cn/gis/

console.log(location.pathname);              // /gis/index.html
console.log(import.meta.env.BASE_URL);       // /  ← 未配置时为根路径

• Fixing only the build base moves the failure from asset 404s to API 404s and looks like a new bug.
• Switching to hash routing to dodge the server fallback breaks deep links and analytics that expect real paths.