fix(a11y): address R9 code-review findings (glass shadow, focus dedup)

- #1: remove the 9 dead `shadow-*` from glass surfaces instead of letting them override the tuned glass
  box-shadow. The @layer components move made a JSX shadow-* win AND atomically drop the glass inset
  top-edge highlight; deleting the (always-dead) utilities keeps the intended glass depth incl. the
  inset sheen. Verified in-browser: a .glass box-shadow again includes its inset segment.
- #3: drop the per-element focus-visible outlines from the rail chrome buttons and SavedViews action
  buttons — the global button:focus-visible fallback already draws the identical 2px accent ring, so
  they were redundant. Verified: the pin button rings from the global rule alone.
- #5: unify the focus-within outline offset (offset-2) on the SearchBar and ShareDialog pills.
- #2 (double outline on the pill when an inner button is focused): NOT fixed — the clean fix
  (has-[input:focus] so only the input rings the pill) does not generate under Tailwind v4 (measured:
  no rule emitted). Kept the working focus-within, which is a11y-correct (every element still shows a
  focus indicator); the overlapping ring is an accepted cosmetic edge-case.
- #4 (weak ring on solid-fill selected items): deferred to R10 with the selected-paint tokenisation.

Gate green (tsc/eslint/prettier/knip/vitest 79).

frontend/src/components/ui/DraftSaveBar.tsx

@@ -37,7 +37,7 @@ export function DraftSaveBar({
   const saving = state === "saving";
   const floating = variant === "floating";
   const wrap = floating
-    ? "fixed bottom-4 left-1/2 -translate-x-1/2 z-rail glass rounded-2xl shadow-lg flex items-center justify-between gap-4 px-4 py-3 w-[min(48rem,calc(100%-2rem))]"
+    ? "fixed bottom-4 left-1/2 -translate-x-1/2 z-rail glass rounded-2xl flex items-center justify-between gap-4 px-4 py-3 w-[min(48rem,calc(100%-2rem))]"
     : "flex items-center justify-between gap-3 border-t border-border/60 px-4 py-3 bg-card/40";
   // The floating variant is fixed to the viewport but renders from a page inside the page
   // scroller, so it goes to <body> — otherwise the scroller's stacking context (its edge-fade