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/PlexPlayerSettings.tsx

@@ -42,7 +42,7 @@ export function PlexPlayerSettings(props: {
       ref={menuRef}
       onWheel={(e) => e.stopPropagation()}
       onClick={(e) => e.stopPropagation()}
-      className="border border-white/15 bg-neutral-900/95 absolute bottom-full right-0 mb-2 w-80 rounded-xl p-2 text-sm text-white shadow-2xl"
+      className="border border-white/15 bg-media-chrome/95 absolute bottom-full right-0 z-menu mb-2 w-80 rounded-xl p-2 text-sm text-white shadow-2xl"
     >
       <div className="mb-1.5 flex gap-1">
         {settingsTabs.map((tab) => (