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/vendors/route.ts

@@ -0,0 +1,54 @@
+import { NextResponse } from "next/server"
+import { asc, eq } from "drizzle-orm"
+import { db } from "@/lib/db"
+import { vendors } from "@/lib/db/schema"
+import { getSessionUser } from "@/lib/session"
+import { vendorSchema } from "@/lib/validations"
+import { ownsProperty } from "@/lib/db/ownership"
+
+export async function GET() {
+  const user = await getSessionUser()
+  if (!user) return NextResponse.json({ error: "Unauthorized" }, { status: 401 })
+
+  const data = await db
+    .select()
+    .from(vendors)
+    .where(eq(vendors.user_id, user.id))
+    .orderBy(asc(vendors.name))
+
+  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 = vendorSchema.safeParse(body)
+  if (!parsed.success) {
+    return NextResponse.json({ error: parsed.error.issues[0]?.message ?? "Invalid input" }, { status: 400 })
+  }
+
+  if (!(await ownsProperty(user.id, parsed.data.property_id))) {
+    return NextResponse.json({ error: "Invalid reference" }, { status: 403 })
+  }
+
+  try {
+    const [data] = await db
+      .insert(vendors)
+      .values({
+        user_id: user.id,
+        name: parsed.data.name,
+        trade: parsed.data.trade || null,
+        phone: parsed.data.phone || null,
+        email: parsed.data.email || null,
+        notes: parsed.data.notes || null,
+        property_id: parsed.data.property_id || null,
+      })
+      .returning()
+
+    return NextResponse.json(data)
+  } catch (e) {
+    return NextResponse.json({ error: (e as Error).message }, { status: 500 })
+  }
+}