A flex item's background across the page it overflows onto

The green footer below is a flex-direction:column item anchored to the bottom of its container via margin-top:auto - the same pattern the invoice showcase uses. Its own committed height (12mm) is pinned once, up front, but its paragraphs need more room than that, so they spill onto the next page. The footer's background and border now continue there instead of stopping after page 1.