[SD-1452] Add 301 redirect for site-prefixed URLs

[vincent-gao]

Jira

https://digital-vic.atlassian.net/browse/SD-1452

details

• /site-{id}/... path aliases are valid Drupal routes but should not appear in search engine results.
• Added an EventSubscriber that 301 redirects anonymous requests from /site-{id}/... to the clean alias path (without the prefix)
• Logged-in CMS users are not affected (detected via Drupal session cookie)
• API requests (JSON API, Tide API) are not affected

❯ curl -I http://content-sdp.docker.internal:8888/api/v1/route\?path\=/site-4/best-start-best-life-reforms\&site\=4
HTTP/1.1 301 Moved Permanently
Server: openresty
Content-Type: text/html; charset=utf-8
Content-Length: 646
Connection: keep-alive
Date: Mon, 06 Apr 2026 22:58:19 GMT
location: /api/v1/route?path=%2Fbest-start-best-life-reforms&site=4
.
.
.
X-Sdp-App-Type: tide