fix: og image generation

app/letters/year/[year]/page.tsx

@@ -1,9 +1,23 @@
 export const dynamic = "force-dynamic";
 
+import type { Metadata } from "next";
 import { notFound } from "next/navigation";
 import { getLettersByYear } from "@/lib/letters";
+import { ogForLettersByYear } from "@/lib/og";
 import { YearMonthBrowser } from "./year-month-browser";
 
+export async function generateMetadata({
+  params,
+}: {
+  params: Promise<{ year: string }>;
+}): Promise<Metadata> {
+  const { year: yearStr } = await params;
+  const year = parseInt(yearStr, 10);
+  if (isNaN(year)) return {};
+  const letters = await getLettersByYear(year);
+  return ogForLettersByYear(year, letters.length);
+}
+
 export default async function LettersByYearPage({
   params,
 }: {