fix(frontend): finish the token migration — raw grey classes -> theme tokens

UI_REDESIGN chunk 4 was never finished: 39 app/component files still used
raw Tailwind greys, kept readable in light mode only by the !important
override sheet. In dark mode text-gray-600 is ~2.3:1 on surface, and the
light override maps it to #94a3b8 (~2.6:1 on white) — unreadable in both.

Mechanical mapping (886 classes): gray-100/200 -> ink, 300/400 -> ink-2,
500/600/700 -> ink-muted, bg 950/900/800 -> page/surface/raised,
border 800 -> line, 700/600 -> line-strong, plus hover/divide/placeholder.
Alpha suffixes kept (tokens are color-mix, so /60 works). bg-gray-700,
text-white and marketing pages left alone. text-[9px] -> text-[10px].

Frontend unverified: no Node on the authoring box (#207).

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

drb-frontend/app/settings/layout.tsx

@@ -43,15 +43,15 @@ export default function SettingsLayout({ children }: { children: React.ReactNode
         description="Organization profile, team access, node ownership, API keys, and billing."
       />
 
-      <div className="flex flex-wrap gap-1 bg-gray-900 border border-gray-800 rounded-lg p-1 w-fit max-w-full overflow-x-auto">
+      <div className="flex flex-wrap gap-1 bg-surface border border-line rounded-lg p-1 w-fit max-w-full overflow-x-auto">
         {[...TABS, ...(isAdmin ? ADMIN_TABS : [])].map((t) => (
           <Link
             key={t.href}
             href={t.href}
             className={`text-sm font-mono px-4 py-1.5 rounded-md transition-colors whitespace-nowrap ${
               pathname === t.href || pathname.startsWith(t.href + "/")
-                ? "bg-gray-800 text-white"
-                : "text-gray-500 hover:text-gray-300"
+                ? "bg-raised text-white"
+                : "text-ink-muted hover:text-ink"
             }`}
           >
             {t.label}