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/route.ts

@@ -3,18 +3,21 @@ import { and, desc, eq } from "drizzle-orm"
 import { db } from "@/lib/db"
 import { notifications, rent_payments, maintenance_requests } from "@/lib/db/schema"
 import { getSessionUser } from "@/lib/session"
-import { sendEmail, rentDueReminderHtml, rentOverdueHtml, maintenanceUpdateHtml } from "@/lib/email/send"
+import { sendEmail, rentDueReminderHtml, maintenanceUpdateHtml } from "@/lib/email/send"
 import { formatCurrency, formatDate } from "@/lib/utils"
+import { getEffectiveOwnerId, getAccountContext } from "@/lib/account"
 
 export async function GET() {
   const user = await getSessionUser()
   if (!user) return NextResponse.json({ error: "Unauthorized" }, { status: 401 })
 
+  const ownerId = await getEffectiveOwnerId(user.id)
+
   try {
     const data = await db
       .select()
       .from(notifications)
-      .where(eq(notifications.user_id, user.id))
+      .where(eq(notifications.user_id, ownerId))
       .orderBy(desc(notifications.sent_at))
       .limit(50)
 
@@ -28,6 +31,10 @@ export async function POST(request: Request) {
   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 })
+
   const body = await request.json() as {
     type: string
     payment_id?: string
@@ -38,7 +45,7 @@ export async function POST(request: Request) {
 
   if (body.type === "rent_reminder" && body.payment_id) {
     const payment = await db.query.rent_payments.findFirst({
-      where: and(eq(rent_payments.id, body.payment_id), eq(rent_payments.user_id, user.id)),
+      where: and(eq(rent_payments.id, body.payment_id), eq(rent_payments.user_id, ownerId)),
       with: {
         tenant: { columns: { first_name: true, last_name: true, email: true } },
         property: { columns: { name: true } },
@@ -64,19 +71,22 @@ export async function POST(request: Request) {
 
     if (result.success) {
       await db.insert(notifications).values({
-        user_id: user.id,
+        user_id: ownerId,
         type: "rent_reminder",
         recipient_email: payment.tenant.email,
         subject: `Rent Due Reminder — ${payment.property.name}`,
         status: "sent",
-        metadata: { payment_id: body.payment_id },
+        metadata: {
+          payment_id: body.payment_id,
+          body: `Reminder sent to ${payment.tenant.first_name} ${payment.tenant.last_name} for ${formatCurrency(payment.amount)} due ${formatDate(payment.due_date)}.`,
+        },
       })
     }
   }
 
   if (body.type === "maintenance_update" && body.maintenance_id) {
     const req = await db.query.maintenance_requests.findFirst({
-      where: and(eq(maintenance_requests.id, body.maintenance_id), eq(maintenance_requests.user_id, user.id)),
+      where: and(eq(maintenance_requests.id, body.maintenance_id), eq(maintenance_requests.user_id, ownerId)),
       with: {
         tenant: { columns: { first_name: true, last_name: true, email: true } },
       },