Redesign /terms page (#4338)

* Redesign /terms page

* Fix tests

* Remove unused keys

app/views/about/terms.html.haml

@@ -1,8 +1,23 @@
 - content_for :page_title do
   = t('terms.title', instance: site_hostname)
 
-.wrapper
-  - if @instance_presenter.site_terms.present?
-    = raw @instance_presenter.site_terms
-  - else
-    = t('terms.body_html')
+.landing-page
+  .header-wrapper.compact
+    .header
+      .container.links
+        .brand
+          = link_to root_url do
+            = image_tag asset_pack_path('logo_full.svg'), alt: 'Mastodon'
+
+        %ul.nav
+          %li
+            - if user_signed_in?
+              = link_to t('settings.back'), root_url, class: 'webapp-btn'
+            - else
+              = link_to t('auth.login'), new_user_session_path, class: 'webapp-btn'
+          %li= link_to t('about.about_this'), about_more_path
+          %li= link_to t('about.other_instances'), 'https://joinmastodon.org/'
+
+  .extended-description
+    .container
+      = @instance_presenter.site_terms.html_safe.presence || t('terms.body_html')