bingo: build the card from chosen providers

Let visitors tick providers (Yandex, IXcellerate, RTK-DC, Sber, …) and
get the usual 5×5 card made of only those providers' datacenters, first
25 in ranking order, with lines scored as normal. A selection with fewer
than 25 sites leaves the rest of the card empty, so the card is always
5×5. Each provider chip shows crossed/total for the current view.

Datacenters get a provider slug, backfilled from the free-text operator,
guessed for new rows and editable in the admin. Filtered URLs are
noindex with canonical to the plain card.

Assisted-by: Claude:opus-5

views/admin/bingo/edit.erb

@@ -45,6 +45,13 @@
                 <div class="field"><label for="city_<%= l %>">City (<%= l %>)</label><input type="text" id="city_<%= l %>" name="city_<%= l %>" value="<%= @dc[:"city_#{l}"] %>" <%= 'required' if l == 'ru' %> /></div>
             <% end %>
             <div class="field"><label for="operator">Operator</label><input type="text" id="operator" name="operator" value="<%= @dc.operator %>" required /></div>
+            <div class="field">
+                <label for="provider">Provider <span class="optional">(groups the per-provider card)</span></label>
+                <select id="provider" name="provider">
+                    <option value="" <%= 'selected' unless @dc.provider %>>none</option>
+                    <% Bingo::PROVIDERS.each do |slug, names| %><option value="<%= slug %>" <%= 'selected' if @dc.provider == slug %>><%= names['ru'] %></option><% end %>
+                </select>
+            </div>
             <div class="field"><label for="mw">MW <span class="optional">(number or range)</span></label><input type="text" id="mw" name="mw" value="<%= @dc.mw %>" /></div>
             <div class="field">
                 <label for="mw_type">Capacity type</label>