Initial import: property management SaaS + security hardening + admin dashboard

Property Management Network — Next.js 16 (App Router), Better Auth,
Drizzle ORM over PostgreSQL, Stripe, OpenAI, Resend.

Includes:
- Security hardening: access-control/IDOR fixes, TLS-by-default DB layer,
  constant-time cron auth, strict security headers, atomic AI quota gating,
  HTML/email output encoding, demo-backdoor disabled in production.
- Superadmin dashboard at /admin (overview/MRR, server-paginated users with
  ban/impersonate/plan/delete, billing, platform activity + admin audit log,
  AI usage, system health) via the Better Auth admin plugin.
- Seed/migration utility scripts under scripts/.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/not-found.tsx

@@ -0,0 +1,16 @@
+import Link from "next/link"
+
+export default function NotFound() {
+  return (
+    <div className="flex min-h-screen flex-col items-center justify-center bg-[#09090b] text-white">
+      <h1 className="text-6xl font-bold text-indigo-500">404</h1>
+      <p className="mt-4 text-xl text-white/60">Page not found</p>
+      <Link
+        href="/"
+        className="mt-8 rounded-lg bg-indigo-600 px-6 py-3 text-sm font-medium text-white hover:bg-indigo-500 transition-colors"
+      >
+        Go home
+      </Link>
+    </div>
+  )
+}