client: size picker-count buttons from content, not a fixed height

The fixed height: 64px had the same fragility the padding fix in the
previous commit addressed, just on the other axis. Dropped it —
height now comes from line-height + padding like any normal button.
min-height: 44px keeps the established touch-target floor (matches
.qty-btn's documented minimum elsewhere in this file) without pinning
an exact number.

client/src/styles.css

@@ -210,7 +210,23 @@ button.danger { background: #5a2a2a; border-color: #7a3a3a; color: #fff; }
   gap: 8px;
 }
 .picker-count {
-  height: 64px;
+  /* #73: the default button padding (12px 16px) leaves ~16px of content
+     width per cell in this 5-column grid — workable for a single digit
+     ("1".."5") but not the two-character "−1".."−5" remove-row labels,
+     which overflowed into the next cell and got visually clipped by its
+     opaque background. `em` padding (relative to this rule's own
+     font-size) rather than fixed px, so it keeps working if font-size
+     changes instead of quietly re-breaking.
+     mara: "why is the popup not just sized to match the children
+     directly?" — right question, the old fixed `height: 64px` was the
+     same fragility as the old fixed padding, just on the other axis.
+     Dropped it: height now comes from content (line-height) + this
+     padding, same as any normal button. `min-height` keeps it a floor
+     rather than a ceiling — this file's `.qty-btn` already documents
+     44px as the minimum touch target elsewhere, so that's the number
+     to protect, not a target to hit exactly. */
+  min-height: 44px;
+  padding: 0.46em 0.15em;
   font-size: 26px;
   font-weight: 800;
 }