[taskboard] add completion sync APIs

app/api/sync/openclaw/route.ts

@@ -0,0 +1,7 @@
+import { NextResponse } from "next/server";
+
+import { syncOpenClawTasks } from "@/lib/openclaw-sync";
+
+export async function POST() {
+  return NextResponse.json(await syncOpenClawTasks());
+}