consolidate all external links through external_link component

Add icon={false} option to external_link for links with their own
visual indicator. Migrate remaining manual target="_blank" links:
email settings adapter links, product show provider edit, card radio
links, social link cards/icons, page renderer tracking and video
fallback. Every external link in the codebase now goes through the
single component — one place to change rel, target, or sr-only text.

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

lib/berrypod_web/live/admin/email_settings.ex

@@ -268,16 +268,15 @@ defmodule BerrypodWeb.Admin.EmailSettings do
               <div>
                 <h3 class="admin-section-subheading">
                   {adapter.name}
-                  <a
+                  <.external_link
                     :if={adapter.url}
                     href={adapter.url}
-                    target="_blank"
-                    rel="noopener noreferrer"
+                    icon={false}
                     class="admin-link-subtle admin-adapter-link"
-                    aria-label={adapter.name <> " website (opens in new tab)"}
+                    aria-label={adapter.name <> " website"}
                   >
                     &nearr;
-                  </a>
+                  </.external_link>
                 </h3>
                 <p class="admin-section-desc">{adapter.description}</p>
               </div>