fix: lazy-initialize VAPID to avoid build-time crash when env vars absent

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/lib/push.ts

@@ -1,16 +1,21 @@
 import webpush from "web-push";
 import { db, pushSubscriptions, eq } from "@epicure/db";
 
-webpush.setVapidDetails(
-  "mailto:contact@epicure.app",
-  process.env.NEXT_PUBLIC_VAPID_PUBLIC_KEY!,
-  process.env.VAPID_PRIVATE_KEY!
-);
+let vapidInitialized = false;
+function ensureVapid() {
+  if (vapidInitialized) return;
+  const pub = process.env.NEXT_PUBLIC_VAPID_PUBLIC_KEY;
+  const priv = process.env.VAPID_PRIVATE_KEY;
+  if (!pub || !priv) throw new Error("VAPID keys not configured");
+  webpush.setVapidDetails("mailto:contact@epicure.app", pub, priv);
+  vapidInitialized = true;
+}
 
 export async function sendPushNotification(
   userId: string,
   notification: { title: string; body: string; url?: string }
 ): Promise<void> {
+  ensureVapid();
   const subs = await db
     .select()
     .from(pushSubscriptions)