feat: implement the first version of landing page

frontend/src/components/landing/footer.tsx

@@ -0,0 +1,19 @@
+import { useMemo } from "react";
+
+export function Footer() {
+  const year = useMemo(() => new Date().getFullYear(), []);
+  return (
+    <footer className="container-md mx-auto mt-32 flex flex-col items-center justify-center">
+      <hr className="from-border/0 to-border/0 m-0 h-px w-full border-none bg-linear-to-r via-white/20" />
+      <div className="text-muted-foreground container flex h-20 flex-col items-center justify-center text-sm">
+        <p className="text-center font-serif text-lg md:text-xl">
+          &quot;Originated from Open Source, give back to Open Source.&quot;
+        </p>
+      </div>
+      <div className="text-muted-foreground container mb-8 flex flex-col items-center justify-center text-xs">
+        <p>Licensed under MIT License</p>
+        <p>&copy; {year} DeerFlow</p>
+      </div>
+    </footer>
+  );
+}