Respect Safe Area Insets on Fixed Elements

The scope is FIXED elements, and that is the whole point of the rule: normal document flow already stops short of the unsafe regions, so a paragraph does not need this. A `position: fixed` header, bottom bar, FAB or drawer is positioned against the viewport, which extends underneath the notch and the home indicator — so it, and only it, lands in hardware. Requires `viewport-fit=cover` in the viewport meta tag; without it the env() values all resolve to 0 and the rule silently does nothing.

Write the padding as `padding-bottom: env(safe-area-inset-bottom)` (or, keeping the element's own padding, `calc(0.75rem + env(safe-area-inset-bottom))`), and note that `pb-safe` / `pt-safe` are NOT core Tailwind — they come from the tailwindcss-safe-area plugin or a hand-written `@utility`, and they do not exist in this project, so writing them here produces no CSS at all.