Decouple lock-icon fill from nth-child color cycling via :not(.lock-icon),
use subtle --nord3 fill in both themes, add responsive lock sizing, and
bump mobile image heights (72→90px, 48→64px).
Use CSS min() in grid minmax to guarantee 2 tiles side-by-side at
any viewport width. Add responsive breakpoints (560px, 410px) to
progressively shrink SVG height, font size, and spacing.
Add small lock icons in the top right corner of links that require authentication (streaming, family photos, cloud, shopping, family tree, transmission, documents, and audiobooks). The icons use SVG symbol references for efficient reuse and adapt to dark mode automatically.
