fix privacy policy niggles and add last-updated date to legal pages

- Capitalise lead sentence regardless of shop_name value
- Add stripe.com/privacy URL when mentioning Stripe in payment section
- Remove mention of logout from session cookie description
- Make third-party sharing text provider-agnostic (no longer names Printify etc.)
- Add :updated_at block to privacy, delivery, and terms pages showing when
  content last changed — auto-tracked via content hash, so the date advances
  automatically whenever relevant settings change

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/berrypod_web/components/shop_components/content.ex

@@ -926,6 +926,14 @@ defmodule BerrypodWeb.ShopComponents.Content do
     """
   end
 
+  defp rich_text_block(%{block: %{type: :updated_at}} = assigns) do
+    ~H"""
+    <p class="rich-text-updated-at">
+      Last updated: {@block.date}
+    </p>
+    """
+  end
+
   defp rich_text_block(%{block: %{type: :paragraph}} = assigns) do
     ~H"""
     <p class="rich-text-paragraph">