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/api/health/route.ts

@@ -1,6 +1,6 @@
 import { NextResponse } from "next/server"
 
-// Lightweight liveness probe used by the Docker HEALTHCHECK and Coolify.
+// Lightweight liveness probe used by the Docker HEALTHCHECK and App Platform.
 // Intentionally does NOT touch the database — a transient DB blip should not
 // cause the container to be marked unhealthy and restarted.
 export const dynamic = "force-dynamic"