The account switcher now always renders the default (starred) account first
and lets you drag the remaining accounts into any order. Default stays
pinned; only non-default rows are draggable (shown via a grip handle on
hover). Wraps each row in a draggable container and persists the new order
through the existing reorderAccounts store action.
Ordering logic extracted to pure helpers (sortDefaultFirst,
reorderNonDefaultIds) in account-utils with unit tests.
