Add footer with popular package links and navigation

Co-authored-by: oBusk <13413409+oBusk@users.noreply.github.com>

Author: Copilot

src/app/_layout/Footer.tsx

@@ -1,15 +1,84 @@
+import Link from "next/link";
 import { forwardRef, type HTMLAttributes } from "react";
 import { cx } from "^/lib/cva";
 
 interface FooterProps extends HTMLAttributes<HTMLDivElement> {}
 
+const popularPackages = [
+    "react",
+    "next",
+    "vue",
+    "typescript",
+    "express",
+    "lodash",
+    "axios",
+];
+
 const Footer = forwardRef<HTMLDivElement, FooterProps>(
     ({ className, ...props }, ref) => (
         <footer
-            className={cx("flex contain-content", className)}
+            className={cx(
+                "flex flex-col gap-6 border-t border-border py-8",
+                className,
+            )}
             {...props}
             ref={ref}
-        />
+        >
+            <div className="mx-auto w-full max-w-7xl px-4">
+                {/* Popular Packages Section */}
+                <div className="mb-6">
+                    <h3 className="mb-3 text-sm font-semibold uppercase tracking-wider text-muted-foreground">
+                        Popular Packages
+                    </h3>
+                    <div className="flex flex-wrap gap-3">
+                        {popularPackages.map((pkg) => (
+                            <Link
+                                key={pkg}
+                                href={`/${pkg}`}
+                                className="rounded-md border border-border bg-card px-3 py-1.5 text-sm text-foreground transition-colors hover:bg-accent hover:text-accent-foreground"
+                            >
+                                {pkg}
+                            </Link>
+                        ))}
+                    </div>
+                </div>
+
+                {/* Footer Links */}
+                <div className="flex flex-col gap-4 border-t border-border pt-6 sm:flex-row sm:items-center sm:justify-between">
+                    <div className="flex flex-wrap gap-4 text-sm text-muted-foreground">
+                        <Link
+                            href="/-/about"
+                            className="hover:text-foreground hover:underline"
+                        >
+                            About
+                        </Link>
+                        <Link
+                            href="/-/about/api"
+                            className="hover:text-foreground hover:underline"
+                        >
+                            API
+                        </Link>
+                        <Link
+                            href="/-/about/source-trust"
+                            className="hover:text-foreground hover:underline"
+                        >
+                            Source Trust
+                        </Link>
+                        <a
+                            href="https://github.com/oBusk/npm-diff.app"
+                            target="_blank"
+                            rel="noopener noreferrer"
+                            className="hover:text-foreground hover:underline"
+                        >
+                            GitHub
+                        </a>
+                    </div>
+                    <div className="text-sm text-muted-foreground">
+                        © 2026 npm-diff.app
+                    </div>
+                </div>
+            </div>
+        </footer>
     ),
 );
 Footer.displayName = "Footer";