Derive CONVEX_SITE_URL in next.config.ts instead of shell script

Replace the complex vercel-build.sh with a simple derivation in
next.config.ts that converts .convex.cloud to .convex.site at build time.

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

Author: prazgaitis

apps/web/next.config.ts

@@ -1,5 +1,14 @@
 import type { NextConfig } from "next";
 
+// Derive NEXT_PUBLIC_CONVEX_SITE_URL from NEXT_PUBLIC_CONVEX_URL if not set.
+// The site URL is always the cloud URL with ".convex.cloud" → ".convex.site".
+if (!process.env.NEXT_PUBLIC_CONVEX_SITE_URL && process.env.NEXT_PUBLIC_CONVEX_URL) {
+  process.env.NEXT_PUBLIC_CONVEX_SITE_URL = process.env.NEXT_PUBLIC_CONVEX_URL.replace(
+    ".convex.cloud",
+    ".convex.site"
+  );
+}
+
 const nextConfig: NextConfig = {};
 
 export default nextConfig;

apps/web/vercel-build.sh

@@ -1,6 +1,6 @@
 {
   "$schema": "https://openapi.vercel.sh/vercel.json",
-  "buildCommand": "bash vercel-build.sh",
+  "buildCommand": "cd ../../packages/backend && npx convex deploy --cmd 'cd ../../apps/web && npx next build' --cmd-url-env-var-name NEXT_PUBLIC_CONVEX_URL",
   "installCommand": "pnpm install",
   "framework": "nextjs"
 }