Fix #11969

* Add profile directory to web UI

* Add a line of bio to the directory

* Fix account tags not being saved correctly

Regression from f371b32

Fix Tag#discoverable not returning tags where listable is nil instead of true

Add notice when saving hashtags in admin UI

Change public hashtag and directory pages to return 404 for forbidden tags

* Remove unused locale string

Red crosses implied that it was bad/unexpected that certain features
were not enabled. In reality, they are options, so showing a green
or grey power-off icon is more appropriate.

Add status of timeline preview as well

Fix sample accounts changing too frequently due to wrong query

Sample accounts are intended to be sorted by popularity

To better align with the list of hashtags

* 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