Fix access check form: use GET so results render

The access check form POSTed and re-rendered :new with a 200 HTML
response, which Turbo rejects ("Form responses must redirect to
another location"), so the result panel never appeared. Since the
check is a read-only query, switch to a GET form and fold the lookup
into the new action. Results are now bookmarkable via the URL.

Bump version to 0.16.2.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

config/routes.rb

@@ -96,7 +96,6 @@ Rails.application.routes.draw do
     end
     resources :groups
     get "access", to: "access_checks#new"
-    post "access", to: "access_checks#create"
   end
 
   # Render dynamic PWA files from app/views/pwa/* (remember to link manifest in application.html.erb)