Add helpers for ios/android app store links in welcome mailer (#33475)

app/helpers/application_helper.rb

@@ -238,6 +238,14 @@ module ApplicationHelper
     I18n.t 'user_mailer.welcome.hashtags_recent_count', people: number_with_delimiter(people), count: people
   end
 
+  def app_store_url_ios
+    'https://apps.apple.com/app/mastodon-for-iphone-and-ipad/id1571998974'
+  end
+
+  def app_store_url_android
+    'https://play.google.com/store/apps/details?id=org.joinmastodon.android'
+  end
+
   private
 
   def storage_host_var

app/views/application/mailer/_checklist.html.haml

@@ -29,8 +29,8 @@
                     %div
                       - if defined?(show_apps_buttons) && show_apps_buttons
                         .email-welcome-apps-btns
-                          = link_to image_tag(frontend_asset_url('images/mailer-new/store-icons/btn-app-store.png'), alt: t('user_mailer.welcome.apps_ios_action'), width: 120, height: 40), 'https://apps.apple.com/app/mastodon-for-iphone-and-ipad/id1571998974'
-                          = link_to image_tag(frontend_asset_url('images/mailer-new/store-icons/btn-google-play.png'), alt: t('user_mailer.welcome.apps_android_action'), width: 120, height: 40), 'https://play.google.com/store/apps/details?id=org.joinmastodon.android'
+                          = link_to image_tag(frontend_asset_url('images/mailer-new/store-icons/btn-app-store.png'), alt: t('user_mailer.welcome.apps_ios_action'), width: 120, height: 40), app_store_url_ios
+                          = link_to image_tag(frontend_asset_url('images/mailer-new/store-icons/btn-google-play.png'), alt: t('user_mailer.welcome.apps_android_action'), width: 120, height: 40), app_store_url_android
                       - elsif defined?(button_text) && defined?(button_url) && defined?(checked) && !checked
                         = render 'application/mailer/button', text: button_text, url: button_url, has_arrow: false
                     /[if mso]

app/views/user_mailer/welcome.text.erb

@@ -30,8 +30,8 @@
 
 5. <%= t('user_mailer.welcome.apps_title') %>
    <%= t('user_mailer.welcome.apps_step') %>
-   * iOS: https://apps.apple.com/app/mastodon-for-iphone-and-ipad/id1571998974
-   * Android: https://play.google.com/store/apps/details?id=org.joinmastodon.android
+   * iOS: <%= app_store_url_ios %>
+   * Android: <%= app_store_url_android %>
 
 ---