fix(design): rating and live colour tokens, the player's menus over its notices, the info overlay on a light theme (E28)

- F16: --rating (theme-scoped gold, 4.5:1 on the page and its chip), --rating-media, --live/--live-fg,
  --media-chrome replace 14 palette literals; a lint rule refuses palette classes; the theme contract
  measures them.
- The Plex player's notices drew over its open settings/tracks popovers: notices z-base, popovers z-menu.
- The player's info overlay rendered theme tokens on its always-dark panel: on a light theme the score
  (2.6:1), collection years (3.2:1) and cast initials (1.05:1) were unreadable; onDark variants now.
- The lint-rule contract tests share one ESLint with a one-off warm-up (a cold first lint took 8 s,
  past vitest's 5 s).

frontend/src/components/PlayerModal.tsx

@@ -653,7 +653,7 @@ export default function PlayerModal({
             {(maximized || isFullscreen) && (
               <div
                 onClick={(e) => e.stopPropagation()}
-                className="absolute inset-x-0 bottom-0 z-menu flex h-14 items-center justify-start gap-x-3 overflow-x-auto border-t border-white/10 bg-neutral-950/95 px-3 text-sm text-white"
+                className="absolute inset-x-0 bottom-0 z-menu flex h-14 items-center justify-start gap-x-3 overflow-x-auto border-t border-white/10 bg-media-chrome/95 px-3 text-sm text-white"
               >
                 {hasQueue && (
                   <>