QuotaCardGrid stacked every provider group vertically in a single
flex flex-col container, and each group's own card grid didn't go
multi-column until the md breakpoint. Provider groups now flow into a
2-column CSS multi-column layout on very wide (2xl) screens instead of
an unconditional vertical stack, and each group's card grid starts at
2 columns immediately, filling horizontal whitespace sooner on
narrower-but-not-mobile viewports.
Regression guard: tests/unit/quota-card-grid-horizontal-layout.test.ts
6d3d122b84