Add login page docs hint (#20619)

* add config field

* add endpoint

* set config var when onboarding

* add no auth exception to nginx config

* form changes and i18n

* clean up

docker/main/rootfs/usr/local/nginx/conf/nginx.conf

@@ -274,6 +274,18 @@ http {
                 include proxy.conf;
             }
 
+            # Allow unauthenticated access to the first_time_login endpoint
+            # so the login page can load help text before authentication.
+            location /api/auth/first_time_login {
+                auth_request off;
+                limit_except GET {
+                    deny all;
+                }
+                rewrite ^/api(/.*)$ $1 break;
+                proxy_pass http://frigate_api;
+                include proxy.conf;
+            }
+
             location /api/stats {
                 include auth_request.conf;
                 access_log off;