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/notifications/read/route.ts

@@ -3,16 +3,21 @@ import { and, eq } from "drizzle-orm"
 import { db } from "@/lib/db"
 import { notifications } from "@/lib/db/schema"
 import { getSessionUser } from "@/lib/session"
+import { getAccountContext } from "@/lib/account"
 
 // PATCH /api/notifications/read — mark all of the user's notifications as read.
 export async function PATCH() {
   const user = await getSessionUser()
   if (!user) return NextResponse.json({ error: "Unauthorized" }, { status: 401 })
 
+  const ctx = await getAccountContext(user.id)
+  const ownerId = ctx.ownerId
+  if (!ctx.canWrite) return NextResponse.json({ error: "Forbidden" }, { status: 403 })
+
   await db
     .update(notifications)
     .set({ read: true })
-    .where(and(eq(notifications.user_id, user.id), eq(notifications.read, false)))
+    .where(and(eq(notifications.user_id, ownerId), eq(notifications.read, false)))
 
   return NextResponse.json({ ok: true })
 }