fix(web): all accent text and icons use accent-fg (#5318)

The raw accent fails AA as text on every dark surface, not only on its
own tint: 3.04:1 on the page, 2.70 on iron, 2.21 on slate, against 4.5.
accent-fg (the house formula, 45% toward parchment) measures 5.62 at
worst across both modes. The operator chose the readable colour over the
signature teal for text, on 2026-10-08.

- 36 sites swap. They are 35 Tailwind uses: links, "Now playing", the
  ingest progress line, active shuffle/repeat, the liked heart, the app
  download icon and its hover. The last is the alphabet rail's pending
  spinner in CSS. Icons follow the text: as graphics they need only
  3:1, and the raw accent misses even that on iron.
- check-tint-contrast adds accent to TEXT_NEVER_RAW, so a new raw
  text-accent or color: var(--fs-accent) fails the web lane. Run against
  the files before the swap, it finds all 36. Borders, rings and fills
  keep the raw accent.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/lib/components/MobileAppDownload.svelte

@@ -48,9 +48,9 @@
     <a
       href={info.apkUrl}
       download="minstrel.apk"
-      class="mobile-app-download flex items-center gap-3 rounded-md border border-border bg-surface px-3 py-2 text-sm text-text-primary no-underline transition-colors hover:bg-surface-hover hover:text-accent focus-visible:ring-2 focus-visible:ring-accent"
+      class="mobile-app-download flex items-center gap-3 rounded-md border border-border bg-surface px-3 py-2 text-sm text-text-primary no-underline transition-colors hover:bg-surface-hover hover:text-accent-fg focus-visible:ring-2 focus-visible:ring-accent"
     >
-      <Smartphone size={18} strokeWidth={1.5} class="shrink-0 text-accent" />
+      <Smartphone size={18} strokeWidth={1.5} class="shrink-0 text-accent-fg" />
       <span class="flex flex-col leading-tight">
         <span class="font-medium">Get the Android app</span>
         <span class="text-xs text-text-secondary">