Per review: remove the assumption that exactly 5 rows fill the visible area.
grid-auto-rows: minmax(96px, 1fr) — rows are at least 96px (the touch-target
size used elsewhere in this file), equal height, and stretch evenly to fill
leftover space when there's room; when there isn't (more rows than fit), every
row stays at the 96px floor and the grid scrolls instead of shrinking rows to
squeeze them in. Smaller floor (80px) in the <=480px media query to match the
already-smaller mobile font sizes there.
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