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>

next.config.ts

@@ -6,7 +6,7 @@ import type { NextConfig } from "next";
 // would conflict with the middleware, so it is intentionally omitted below.
 const nextConfig: NextConfig = {
   // Emit a self-contained server bundle at .next/standalone so the Docker
-  // image (used by Coolify) ships only the files needed to run `node server.js`.
+  // image (deployed to DigitalOcean App Platform) ships only the files needed to run `node server.js`.
   output: "standalone",
 
   // Strict security headers applied to every route.