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/WatchPage.tsx

@@ -192,7 +192,7 @@ export default function WatchPage() {
                 placeholder={T.passwordPlaceholder}
                 className="w-full rounded-lg bg-surface border border-border px-3 py-2 text-sm outline-hidden focus:ring-2 focus:ring-accent/40"
               />
-              {error && <div className="text-sm text-red-400 mt-2">{error}</div>}
+              {error && <div className="text-sm text-danger mt-2">{error}</div>}
               <button
                 onClick={unlock}
                 disabled={!password || unlocking}