feat(theme): R10 S1 — semantic status colors (danger/warn/success)

Add theme-scoped --danger/--warn/--success (+ -fg) tokens wired into the v4
@theme inline, replacing ~110 raw red/amber/emerald/green palette refs across
34 files. Fixes light-theme contrast failures (fixed Tailwind shades fell to
~1.7-3:1 on white). Status colors are scheme-independent — recognised by hue,
shifting only by theme to hold contrast (bright on dark bg, darkened on light).
Solid fills use the paired -fg text; @source inline guarantees the full -fg set
exists. IMDb rating gold kept as a deliberate decorative non-status exception.

frontend/src/components/QueryState.tsx

@@ -44,7 +44,7 @@ export function StateMessage({
       aria-live={tone === "error" ? "assertive" : "polite"}
     >
       <span className="inline-flex items-center gap-2 text-center">
-        {tone === "error" && <AlertTriangle className="w-4 h-4 shrink-0 text-red-400" />}
+        {tone === "error" && <AlertTriangle className="w-4 h-4 shrink-0 text-danger" />}
         {children}
       </span>
       {onRetry && (