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/VideoEditor.tsx

@@ -460,7 +460,7 @@ export default function VideoEditor({ job, onClose }: { job: DownloadJob; onClos
                     e.stopPropagation();
                     deleteBoundary(bi);
                   }}
-                  className="absolute top-0 -right-2 p-0.5 rounded-full bg-black/70 text-muted hover:text-red-400"
+                  className="absolute top-0 -right-2 p-0.5 rounded-full bg-black/70 text-muted hover:text-danger"
                   title={t("editor.removeCut")}
                 >
                   <X className="w-3 h-3" />