Add Toolbox promo card to student dashboard (Мои курсы)

Entry point into /tools alongside courses, per gate #3 decision.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/tools/ToolboxPromoCard.tsx

@@ -0,0 +1,26 @@
+import Link from "next/link";
+import { Wrench } from "lucide-react";
+
+// Промо-карточка Toolbox для раздела «Мои курсы» — точка входа в /tools.
+export function ToolboxPromoCard() {
+  return (
+    <Link
+      href="/tools"
+      className="card-aubade p-5 flex items-center gap-4 no-underline"
+      style={{ background: "var(--accent)" }}
+    >
+      <Wrench size={28} style={{ color: "var(--foreground)", flexShrink: 0 }} />
+      <div className="flex-1">
+        <h2 className="font-bold text-lg leading-tight" style={{ color: "var(--foreground)" }}>
+          Инструменты Obsidian
+        </h2>
+        <p className="text-sm" style={{ color: "var(--foreground)" }}>
+          Генераторы синтаксиса: callout-CSS, YAML-frontmatter, темы, Style Settings.
+        </p>
+      </div>
+      <span className="text-sm font-bold whitespace-nowrap" style={{ color: "var(--foreground)" }}>
+        Открыть →
+      </span>
+    </Link>
+  );
+}