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

config/locales/en.yml

@@ -48,6 +48,7 @@ en:
       other: Followers
     following: Following
     joined: Joined %{date}
+    link_verified_on: Ownership of this link was checked on %{date}
     media: Media
     moved_html: "%{name} has moved to %{new_profile_link}:"
     network_hidden: This information is not available
@@ -460,7 +461,7 @@ en:
     warning: Be very careful with this data. Never share it with anyone!
     your_token: Your access token
   auth:
-    agreement_html: By signing up you agree to follow <a href="%{rules_path}">the rules of the instance</a> and <a href="%{terms_path}">our terms of service</a>.
+    agreement_html: By clicking "Sign up" below you agree to follow <a href="%{rules_path}">the rules of the instance</a> and <a href="%{terms_path}">our terms of service</a>.
     change_password: Password
     confirm_email: Confirm email
     delete_account: Delete account
@@ -921,3 +922,6 @@ en:
     otp_lost_help_html: If you lost access to both, you may get in touch with %{email}
     seamless_external_login: You are logged in via an external service, so password and e-mail settings are not available.
     signed_in_as: 'Signed in as:'
+  verification:
+    explanation_html: 'You can <strong>verify yourself as the owner of the links in your profile metadata</strong>. For that, the linked website must contain a link back to your Mastodon profile. The link back <strong>must</strong> have a <code>rel="me"</code> attribute. The text content of the link does not matter. Here is an example:'
+    verification: Verification