Restyle mobile Menu page (Screens 1-3) for Minimal Light

Restyles the existing 3-screen mobile menu system (category list, filtered list, single-product view) to match Minimal Light — Screen 1's category list converted from vertical rows to a circular 4-column grid, Screens 2-3 get palette/typography updates. All underlying logic (screen transitions, stepper, attribute selection, add-to-cart) is completely untouched — verified against the same precision standard as the v3.18.22 modal reskin. Khana Khazana mobile unaffected.