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/PlexPlayer.tsx

@@ -1095,7 +1095,7 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
       {!ready && (
         <div className="absolute inset-0 grid place-items-center px-6 text-center text-sm pointer-events-none">
           {loadError ? (
-            <span className="max-w-md text-red-300">{loadError}</span>
+            <span className="max-w-md text-danger">{loadError}</span>
           ) : (
             <span className="text-white/70">{t("plex.player.loading")}</span>
           )}
@@ -1235,7 +1235,7 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
           {detail?.markers.map((m, i) => (
             <div
               key={i}
-              className="absolute inset-y-0 bg-amber-400/50"
+              className="absolute inset-y-0 bg-warn/50"
               style={{
                 left: `${(m.start_s / duration) * 100}%`,
                 width: `${((m.end_s - m.start_s) / duration) * 100}%`,