Authorize admin by username jmartin only

Drop group membership checks; trust Authelia Remote-User when it
equals the configured ADMIN_USERS list (default: jmartin).

.env.example

@@ -25,8 +25,8 @@ IMGPROXY_KEY=
 IMGPROXY_SALT=
 
 # Auth — Authelia Remote-User trust
-# Comma-separated groups allowed to access admin (empty = any authenticated user)
-ADMIN_GROUPS=lldap_admin,admin,portfolio_admin
+# Comma-separated usernames allowed for admin (groups ignored)
+ADMIN_USERS=jmartin
 # When true, require Remote-User header for /api/v1/admin/* (disable only for local dev)
 REQUIRE_REMOTE_USER=true