feat(frontend): rich OG metadata + dynamic page titles across all routes

thoughts-frontend/app/page.tsx

@@ -1,3 +1,4 @@
+import type { Metadata } from "next";
 import { cookies } from "next/headers";
 import {
   getFeed,
@@ -26,6 +27,11 @@ import {
 } from "@/components/ui/pagination";
 import { redirect } from "next/navigation";
 
+export const metadata: Metadata = {
+  title: "Home",
+  description: "Your home timeline — thoughts from people you follow",
+};
+
 export default async function Home({
   searchParams,
 }: {