Fix routes to manifest and service-worker, rename controller

app/controllers/pwa_controller.rb

@@ -1,12 +1,8 @@
 class PwaController < ApplicationController
-  allow_unauthenticated_access
+  require_untenanted_access
   skip_forgery_protection
 
   # We need a stable URL at the root, so we can't use the regular asset path here.
   def service_worker
   end
-
-  # Need ERB interpolation for paths, so can't use asset path here either.
-  def manifest
-  end
-end
+end