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/vendors/route.ts

@@ -5,15 +5,18 @@ import { vendors } from "@/lib/db/schema"
 import { getSessionUser } from "@/lib/session"
 import { vendorSchema } from "@/lib/validations"
 import { ownsProperty } from "@/lib/db/ownership"
+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)
+
   const data = await db
     .select()
     .from(vendors)
-    .where(eq(vendors.user_id, user.id))
+    .where(eq(vendors.user_id, ownerId))
     .orderBy(asc(vendors.name))
 
   return NextResponse.json(data)
@@ -23,13 +26,17 @@ 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()
   const parsed = vendorSchema.safeParse(body)
   if (!parsed.success) {
     return NextResponse.json({ error: parsed.error.issues[0]?.message ?? "Invalid input" }, { status: 400 })
   }
 
-  if (!(await ownsProperty(user.id, parsed.data.property_id))) {
+  if (!(await ownsProperty(ownerId, parsed.data.property_id))) {
     return NextResponse.json({ error: "Invalid reference" }, { status: 403 })
   }
 
@@ -37,7 +44,7 @@ export async function POST(request: Request) {
     const [data] = await db
       .insert(vendors)
       .values({
-        user_id: user.id,
+        user_id: ownerId,
         name: parsed.data.name,
         trade: parsed.data.trade || null,
         phone: parsed.data.phone || null,