The reserve modal delegated to a nested ActionButton, whose own flow modal
opened over it - the username field ended up behind it and the request preview
came through empty on confirm. Replace it with a modal that owns its username
and reason fields and posts the reserve/unreserve command directly. Render the
@ prefix as text, not an icon.
Move "Reserve username" into a modal opened from the page actions, and keep a
single search toolbar in the query panel, so the page matches Collectible
Usernames instead of stacking two toolbars with an unconstrained input.
