style(mobile/map): resize FAB from 84 to 60 px

84 felt overpowering next to the map overlay pills. 60 keeps
the button prominent without dominating the screen. The xl
size variant no longer corresponds to exactly 150 % of md —
drops the stale comment.

Author: Aqib-Rime

apps/mobile/components/ui/icon-button.tsx

@@ -9,7 +9,6 @@ const iconButtonVariants = cva("items-center justify-center", {
     size: {
       sm: "h-10 w-10",
       md: "h-14 w-14",
-      // 150% of md — used for the floating action button on the map.
       xl: "size-[60px]",
     },
     shape: {