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/PlexCollectionEditor.tsx

@@ -193,7 +193,7 @@ export default function PlexCollectionEditor({
                 <button
                   onClick={() => removeCollection(c.id, c.title)}
                   disabled={!!busy}
-                  className="shrink-0 rounded-sm px-1.5 py-0.5 text-xs text-muted hover:text-red-400 disabled:opacity-50"
+                  className="shrink-0 rounded-sm px-1.5 py-0.5 text-xs text-muted hover:text-danger disabled:opacity-50"
                 >
                   {t("plex.collEditor.delete")}
                 </button>