actually fix localhost client support

frontend/src/lib/oauth.ts

···
 ].join(' ')
 const CLIENT_ID = !(import.meta.env.DEV)
     ? `${window.location.origin}/oauth/client-metadata.json`
-    : `http://localhost/oauth/client-metadata.json?scope=${SCOPES}`
+    : `http://localhost/?scope=${SCOPES}`
 const REDIRECT_URI = `${window.location.origin}/`
 
 interface OAuthState {

src/oauth/client.rs

···
             url.scheme() == "http"
                 && url.host_str() == Some("localhost")
                 && url.port().is_none()
-                && url.path().is_empty()
+                // empty path
+                && url.path() == "/"
         } else {
             false
         }