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/DownloadCenter.tsx

@@ -45,9 +45,9 @@ const GiB = 1024 ** 3;
 const STATUS_CLS: Record<string, string> = {
   queued: "text-muted",
   running: "text-accent",
-  paused: "text-amber-400",
-  done: "text-emerald-400",
-  error: "text-red-400",
+  paused: "text-warn",
+  done: "text-success",
+  error: "text-danger",
   canceled: "text-muted",
 };
 
@@ -137,7 +137,7 @@ function IconBtn({
       title={title}
       className={clsx(
         "p-1.5 rounded-md hover:bg-surface text-muted transition",
-        danger ? "hover:text-red-400" : "hover:text-fg",
+        danger ? "hover:text-danger" : "hover:text-fg",
       )}
     >
       {children}
@@ -253,7 +253,7 @@ function DownloadRow({
           {job.status === "error" ? (
             <button
               onClick={() => onShowError?.(job)}
-              className="text-red-400 hover:text-red-300 inline-flex items-center gap-1 truncate"
+              className="text-danger hover:text-danger inline-flex items-center gap-1 truncate"
               title={t("downloads.errors.fail.title")}
             >
               · {t(`downloads.errors.fail.cat.${job.error_code || "unknown"}.short`)}
@@ -492,7 +492,7 @@ function UsageBar() {
       {!u.unlimited && (
         <div className="h-2 rounded-full bg-surface overflow-hidden">
           <div
-            className={clsx("h-full transition-all", pct > 90 ? "bg-red-400" : "bg-accent")}
+            className={clsx("h-full transition-all", pct > 90 ? "bg-danger" : "bg-accent")}
             style={{ width: `${pct}%` }}
           />
         </div>