feat: initial commit — backend API + student cabinet frontend

- Go backend: auth (JWT), points earn/spend, QR token generation,
  partners, admin grant/stats endpoints with chi router
- Next.js 14 frontend: login, student dashboard, transaction history,
  QR display, partners list
- PostgreSQL migrations (4 tables), Redis cache, Docker Compose
- CORS middleware, role-based route protection, Zustand auth store

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/components/ui/Spinner.tsx

@@ -0,0 +1,20 @@
+interface SpinnerProps {
+  size?: 'sm' | 'md' | 'lg';
+  className?: string;
+}
+
+const SIZE_CLASSES = {
+  sm: 'h-4 w-4 border-2',
+  md: 'h-8 w-8 border-2',
+  lg: 'h-12 w-12 border-4',
+};
+
+export function Spinner({ size = 'md', className = '' }: SpinnerProps) {
+  return (
+    <div
+      role="status"
+      aria-label="Загрузка"
+      className={`animate-spin rounded-full border-blue-600 border-t-transparent ${SIZE_CLASSES[size]} ${className}`}
+    />
+  );
+}