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>

lib/hooks/use-warn-unsaved.ts

@@ -0,0 +1,18 @@
+"use client"
+
+import { useEffect } from "react"
+
+/**
+ * Adds a beforeunload warning when the form has unsaved changes.
+ * Pass `isDirty` — set to true as soon as any field changes.
+ */
+export function useWarnUnsaved(isDirty: boolean) {
+  useEffect(() => {
+    if (!isDirty) return
+    function handler(e: BeforeUnloadEvent) {
+      e.preventDefault()
+    }
+    window.addEventListener("beforeunload", handler)
+    return () => window.removeEventListener("beforeunload", handler)
+  }, [isDirty])
+}