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/ResultCard.tsx

@@ -0,0 +1,40 @@
+import type { SearchResult } from "@/lib/mock-data";
+
+interface ResultCardProps {
+  result: SearchResult;
+}
+
+export function ResultCard({ result }: ResultCardProps) {
+  const domain = result.parsed_url[1];
+  const faviconUrl = `https://www.google.com/s2/favicons?domain=${domain}&sz=32`;
+
+  return (
+    <a
+      href={result.url}
+      target="_blank"
+      rel="noopener noreferrer"
+      className="block px-4 py-3 -mx-4 rounded-lg transition-colors hover:bg-result-hover group"
+    >
+      <div className="flex items-center gap-2 mb-1">
+        <img src={faviconUrl} alt="" className="w-4 h-4 rounded-sm" loading="lazy" />
+        <span className="text-xs text-muted-foreground truncate">{result.pretty_url}</span>
+        {result.engines.length > 1 && (
+          <span className="text-[10px] text-muted-foreground/60 ml-auto shrink-0">
+            {result.engines.length} engines
+          </span>
+        )}
+      </div>
+      <h3 className="text-link group-hover:text-link-hover font-medium text-base leading-snug mb-1 line-clamp-1">
+        {result.title}
+      </h3>
+      <p className="text-sm text-muted-foreground leading-relaxed line-clamp-2">
+        {result.content}
+      </p>
+      {result.publishedDate && (
+        <span className="text-xs text-muted-foreground/70 mt-1 inline-block">
+          {new Date(result.publishedDate).toLocaleDateString("en-US", { year: "numeric", month: "short", day: "numeric" })}
+        </span>
+      )}
+    </a>
+  );
+}