🐛 Fix Admin Console URLs escaped twice

The Admin Console location built its proxy_pass target from a capture of
$request_uri, which nginx escapes again when the path has escaped
characters: %XX became %25XX and the query string ended up in the path,
so Admin Console links returned 404. Strip the prefix with a rewrite and
let proxy_pass forward the rewritten URI instead.

AI-assisted-by: Claude
Signed-off-by: David Barragán Merino <david.barragan@kaleidos.net>
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f