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/playlistColumns.tsx

@@ -113,7 +113,7 @@ export function playlistColumns({
           <span
             className={`text-3xs font-semibold uppercase tracking-wide px-1.5 py-0.5 rounded ${
               v.live_status === "live"
-                ? "bg-red-500/90 text-white" /* fixed live-red, not the status token */
+                ? "bg-live text-live-fg" /* the broadcast red, not --danger */
                 : "bg-card border border-border text-muted"
             }`}
           >