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/VideoCard.tsx

@@ -158,8 +158,8 @@ function RowMetaCells({ video }: { video: Video }) {
   // "live" dot and a "stream" dot would be the same dot.
   const status =
     video.live_status === "live"
-      ? // fixed live-red, not the status token — "live" is a broadcast indicator, not an error
-        { Icon: Radio, cls: "text-red-500", label: t("card.live") }
+      ? // the broadcast red, not --danger: "live" is not an error
+        { Icon: Radio, cls: "text-live", label: t("card.live") }
       : video.live_status === "upcoming"
         ? { Icon: Clock, cls: "", label: t("card.upcoming") }
         : video.live_status === "was_live"
@@ -253,7 +253,7 @@ function Thumb({
       ) : video.live_status === "live" || video.live_status === "upcoming" ? (
         <span
           className={`absolute bottom-1.5 right-1.5 text-3xs font-semibold uppercase tracking-wide px-1.5 py-0.5 rounded ${
-            video.live_status === "live" ? "bg-red-500/90 text-white" : "bg-black/80 text-white"
+            video.live_status === "live" ? "bg-live text-live-fg" : "bg-black/80 text-white"
           }`}
         >
           {t(`card.${video.live_status}`)}