Redesign forms, verify link ownership with rel="me" (#8703)

* Verify link ownership with rel="me"

* Add explanation about verification to UI

* Perform link verifications

* Add click-to-copy widget for verification HTML

* Redesign edit profile page

* Redesign forms

* Improve responsive design of settings pages

* Restore landing page sign-up form

* Fix typo

* Support <link> tags, add spec

* Fix links not being verified on first discovery and passive updates

app/workers/verify_account_links_worker.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+class VerifyAccountLinksWorker
+  include Sidekiq::Worker
+
+  sidekiq_options queue: 'pull', retry: false, unique: :until_executed
+
+  def perform(account_id)
+    account = Account.find(account_id)
+
+    account.fields.each do |field|
+      next unless !field.verified? && field.verifiable?
+      VerifyLinkService.new.call(field)
+    end
+
+    account.save! if account.changed?
+  rescue ActiveRecord::RecordNotFound
+    true
+  end
+end