refactor: migrate session usage to better-auth API

src/app/api/ai-event/route.ts

@@ -1,8 +1,11 @@
 import { NextResponse } from "next/server";
 import { auth } from "@/auth";
+import { headers } from "next/headers";
 
 export async function POST(request: Request) {
-	const session = await auth();
+	const session = await auth.api.getSession({
+		headers: await headers(),
+	});
 	
 	if (!session?.user) {
 		return NextResponse.json(