The UI redesign in T401774 calls for the creation timestamp of each key to be displayed on Special:AccountSecurity. Separating this out in its own task because it's a little more complicated for two reasons:

• The creation timestamp is stored in the database, but nothing currently retrieves it. We'll have to retrieve it from the DB somewhere in order to be able to display it.
• Older keys (created before May 2024) have their creation timestamp set to NULL, so we'll have to handle that (presumably by not displaying the "created on" message at all)

Acceptance criteria:

• Creation timestamp is added to the UI
• Nulls are handled in a reasonable way