Change reported media attachments to always be hidden in admin UI (#12879)

Also:

- Fix Mastodon logo not showing up in status embeds
- Fix blurhash not being used in status embeds
- Fix blurhash not being used in admin UI
- Fix autoplay param not working correctly on status embeds

app/views/layouts/admin.html.haml

@@ -1,4 +1,5 @@
 - content_for :header_tags do
+  = render_initial_state
   = javascript_pack_tag 'public', integrity: true, crossorigin: 'anonymous'
 
 - content_for :content do

app/views/layouts/embedded.html.haml

@@ -14,6 +14,10 @@
     = stylesheet_pack_tag Setting.default_settings['theme'], media: 'all'
     = javascript_pack_tag 'common', integrity: true, crossorigin: 'anonymous'
     = javascript_pack_tag "locale_#{I18n.locale}", integrity: true, crossorigin: 'anonymous'
+    = render_initial_state
     = javascript_pack_tag 'public', integrity: true, crossorigin: 'anonymous'
   %body.embed
     = yield
+
+    %div{ style: 'display: none'}
+      = render file: Rails.root.join('app', 'javascript', 'images', 'logo_transparent.svg')