bingo: redirect /en/ to /en, follow the view links

/en/ answered 200 with the same page as /en. The canonical tag covered
it, but a 301 keeps crawlers and shared links on a single URL.

The All / Operational toggle links were rel="nofollow". The filtered
page is already noindex with a canonical back to the locale URL, so
nofollow on our own links only threw away internal link signals.

Assisted-by: Claude:opus-5

views/bingo/index.erb

@@ -5,7 +5,7 @@
     <div class="switches">
       <nav class="toggle" aria-label="<%= t(:view_label) %>">
         <% Bingo::VIEWS.each do |v| %>
-          <a href="<%= card_path(@locale, v) %>" rel="nofollow" <%== 'aria-current="page"' if v == @view %>><%= t(:"view_#{v}") %></a>
+          <a href="<%= card_path(@locale, v) %>" <%== 'aria-current="page"' if v == @view %>><%= t(:"view_#{v}") %></a>
         <% end %>
       </nav>
       <nav class="langs">