feat(admin-ui): shadcn/ui + Tailwind v4 foundation + theme switch

ordinis-admin-ui/src/lib/utils.ts

@@ -0,0 +1,12 @@
+import { type ClassValue, clsx } from 'clsx'
+import { twMerge } from 'tailwind-merge'
+
+/**
+ * Tailwind class merger — combines clsx (conditional classes) + tailwind-merge
+ * (resolves conflicts: e.g. `px-2 px-4` → `px-4`).
+ *
+ * Standard shadcn/ui utility, used by every primitive variant.
+ */
+export function cn(...inputs: ClassValue[]) {
+  return twMerge(clsx(inputs))
+}