Consolidate audit-fixes branch: webhooks, integrations, and deploy hardening

Batch commit of the pending working tree on security/audit-fixes-2026-07.
Major areas:
- Outbound webhooks / Zapier: schema + signed delivery with retries, public
  v1 API (REST-hook subscribe/unsubscribe), settings UI, cron drain.
- Deploy hardening: email via SMTP2GO (Resend fully removed), verified DB TLS
  (DATABASE_SSL=require + DATABASE_CA), storage fails loud in production when
  Spaces is unconfigured instead of silently using ephemeral disk.
- Integrations & features (concurrent work): accounting (QuickBooks/Xero),
  e-signature (DocuSign/Dropbox Sign), PayPal, geocoding/maps, onboarding,
  expanded legal pages.
- DB migrations 0006–0009.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/(dashboard)/settings/demo/page.tsx

@@ -2,7 +2,7 @@ import { seedDemoData, clearDemoData, setTestPlan } from "@/app/actions/seed-dem
 import { eq } from "drizzle-orm"
 import { db } from "@/lib/db"
 import { profiles } from "@/lib/db/schema"
-import { getSessionUser } from "@/lib/session"
+import { getSessionUser, isAdminUser } from "@/lib/session"
 import { redirect, notFound } from "next/navigation"
 import {
   Building2, Users, CreditCard, Wrench,
@@ -30,7 +30,8 @@ export default async function DemoDataPage() {
   const user = await getSessionUser()
   if (!user) redirect("/login")
 
-  if (process.env.NODE_ENV === "production") notFound()
+  // Admin-only testing tool — regular users get a 404 (and never see the nav link).
+  if (!isAdminUser(user)) notFound()
 
   const profile = await db.query.profiles.findFirst({
     where: eq(profiles.id, user.id),