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/route.ts

@@ -0,0 +1,54 @@
+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"
+import { expenseSchema } from "@/lib/validations"
+import { ownsProperty, ownsUnit } from "@/lib/db/ownership"
+
+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 category = searchParams.get("category")
+
+  const data = await db.query.expenses.findMany({
+    where: and(
+      eq(expenses.user_id, user.id),
+      propertyId ? eq(expenses.property_id, propertyId) : undefined,
+      category ? eq(expenses.category, category as typeof expenses.$inferSelect.category) : undefined
+    ),
+    with: {
+      property: { columns: { name: true } },
+      unit: { columns: { unit_number: true } },
+    },
+    orderBy: desc(expenses.expense_date),
+  })
+
+  return NextResponse.json(data)
+}
+
+export async function POST(request: Request) {
+  const user = await getSessionUser()
+  if (!user) return NextResponse.json({ error: "Unauthorized" }, { status: 401 })
+
+  const body = await request.json()
+  const parsed = expenseSchema.safeParse(body)
+  if (!parsed.success) return NextResponse.json({ error: parsed.error.flatten() }, { status: 400 })
+
+  if (
+    !(await ownsProperty(user.id, parsed.data.property_id)) ||
+    !(await ownsUnit(user.id, parsed.data.unit_id))
+  ) {
+    return NextResponse.json({ error: "Invalid reference" }, { status: 403 })
+  }
+
+  const [data] = await db
+    .insert(expenses)
+    .values({ ...parsed.data, user_id: user.id })
+    .returning()
+
+  return NextResponse.json(data, { status: 201 })
+}