Fix #6060

Fixes #6060

* Remove "most popular" tab from profile directory, add responsive design

* Remove unused translations

* Add instance-wide setting to disable profile directory

Fixes #9496

When the profile directory is disabled:
- The “discoverable” setting is hidden from users
- The “profile directory” link is not shown on public pages
- /explore returns 404

* Move Setting.profile_directory check to a before_action filter

Fix #5578

Regression from #8942

* Change documentation URL

* Fix hardcoded documentation URL in locales

* Revert "Fix some icon names changed by the Font Awesome 5. (#8796)"

This reverts commit 3f9ec3de82.

* Revert "Migrate to font-awesome 5.0. (#8799)"

This reverts commit 8bae14591b.

* Revert "Fix some icons names, unavailable in fontawesome5 (free license). (#8792)"

This reverts commit b9c727a945.

* Revert "Update the icon name changed by the Font Awesome 5. (#8776)"

This reverts commit 17af4d27da.

* Revert "Add bot icon to bot avatars and migrate to newer version of Font Awesome (#8484)"

This reverts commit 4b794e134d.

* Add force_login option to OAuth authorize page

For when a user needs to sign into an app from multiple accounts
on the same server

* When logging out from modal header, redirect back after re-login

Add forgotten custom CSS admin setting strings

Fix #3894

Fix #8393

Fix #8269

* Add remote interaction dialog for toots

* Change AuthorizeFollow into AuthorizeInteraction, support statuses

* Update brakeman.ignore

* Adjust how interaction buttons are display on public pages

* Fix tests

This is a bit hackish. The best way would simply to somehow
use Mastodon's ApplicationController with `use_pack 'error'` from
the Rake task, but I'm not sure how to do that.

* Add preference to hide following/followers lists

- Public pages
- ActivityPub collections (does not return pages but does give total)
- REST API (unless it's your own) (does not federate)

Fix #6901

* Add preference

* Add delegation

* Fix issue

* Fix issue

- Add missing meta description to profiles
- Add canonical rel link to landing page
- Remove linebreaks from title tags
- Add username to profile title
- Add toots/following/followers to profile description tags
- Add next/prev rel links to profiles
- Do not index follower/following variants of profiles

* Update public.html.haml

* Update auth.html.haml

* Update modal.html.haml

* Use PNG images in HTML e-mails

* Make webpack use URLs with host so fonts load inside HTML e-mails

Convert this back to a relative URL in the premailer CSS loader
since local requests are quicker

* Improve responsive design

* Add missing PNG icon

* Remove onboarding modal

* Welcome e-mail

* Send welcome e-mail after confirmation

* Remove obsolete translations

- premailer gem to turn CSS into inline styles automatically
- rework UserMailer templates
- reword UserMailer templates

* delete X-UA-Compatible

* undo

* restore

* Reduce motion for boost animation

Fixes #5833

* Fix ternary expression

- 500.html generated with admin-set default locale if set
- Error page `<title>` includes Mastodon site title
- 500 title changed to "This page is not
  correct" (ref: <https://www.youtube.com/watch?v=2VCAP_seh1A>)
- 500 content appended with "on our end" to make clear it's
  not user's fault