fix: encode tokens to url-safe strings

lib/comfycamp_web/controllers/oauth_controller.ex

@@ -102,8 +102,8 @@ defmodule ComfycampWeb.OauthController do
     {:ok, signed_id_token} = Token.sign(id_token)
 
     render(conn, :token,
-      access_token: access_token,
-      refresh_token: refresh_token,
+      access_token: Base.url_encode64(access_token),
+      refresh_token: Base.url_encode64(refresh_token),
       id_token: signed_id_token
     )
   end