#1 DocumentPreview renders the page pager for every PDF (disabled at the ends),
not only multi-page ones — so the control is visible on single-page invoices.
#2 Clicking a categorized (unpaid) invoice opens the Mark-paid dialog; new →
categorize, paid/declined/duplicate → view.
#3 A paid row no longer shows two 'Paid' chips — the front badge is the status,
and the right action becomes a quiet 'Mark unpaid' (revert).