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/api/expenses/export/route.ts

@@ -0,0 +1,48 @@
+import { NextResponse } from "next/server"
+import { and, desc, eq } from "drizzle-orm"
+import { db } from "@/lib/db"
+import { expenses } from "@/lib/db/schema"
+import { getSessionUser } from "@/lib/session"
+
+export async function GET(request: Request) {
+  const user = await getSessionUser()
+  if (!user) return NextResponse.json({ error: "Unauthorized" }, { status: 401 })
+
+  const { searchParams } = new URL(request.url)
+  const propertyId = searchParams.get("property_id")
+
+  const data = await db.query.expenses.findMany({
+    where: and(
+      eq(expenses.user_id, user.id),
+      propertyId ? eq(expenses.property_id, propertyId) : undefined
+    ),
+    with: {
+      property: { columns: { name: true } },
+    },
+    orderBy: desc(expenses.expense_date),
+  })
+
+  const rows = [
+    ["Date", "Description", "Category", "Amount", "Property", "Vendor", "Recurring", "Recurrence", "Notes"],
+    ...data.map((e) => [
+      e.expense_date,
+      e.description,
+      e.category,
+      e.amount,
+      e.property?.name ?? "",
+      e.vendor ?? "",
+      e.is_recurring ? "Yes" : "No",
+      e.recurrence ?? "",
+      e.notes ?? "",
+    ]),
+  ]
+
+  const csv = rows.map((r) => r.map((v) => `"${String(v).replace(/"/g, '""')}"`).join(",")).join("\n")
+
+  return new Response(csv, {
+    headers: {
+      "Content-Type": "text/csv",
+      "Content-Disposition": `attachment; filename="expenses-${new Date().toISOString().slice(0, 10)}.csv"`,
+    },
+  })
+}