feat: add frontend source code

Add search-zen-50 React SPA source code to frontend/ directory.
Build artifacts (dist, node_modules, lock files) are gitignored.

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

frontend/src/components/ui/label.tsx

@@ -0,0 +1,17 @@
+import * as React from "react";
+import * as LabelPrimitive from "@radix-ui/react-label";
+import { cva, type VariantProps } from "class-variance-authority";
+
+import { cn } from "@/lib/utils";
+
+const labelVariants = cva("text-sm font-medium leading-none peer-disabled:cursor-not-allowed peer-disabled:opacity-70");
+
+const Label = React.forwardRef<
+  React.ElementRef<typeof LabelPrimitive.Root>,
+  React.ComponentPropsWithoutRef<typeof LabelPrimitive.Root> & VariantProps<typeof labelVariants>
+>(({ className, ...props }, ref) => (
+  <LabelPrimitive.Root ref={ref} className={cn(labelVariants(), className)} {...props} />
+));
+Label.displayName = LabelPrimitive.Root.displayName;
+
+export { Label };