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/integrations/[provider]/connect/route.ts

@@ -0,0 +1,33 @@
+import { NextResponse } from "next/server"
+import { getSessionUser } from "@/lib/session"
+import { getAccountContext } from "@/lib/account"
+import { getProvider } from "@/lib/accounting"
+import { signState } from "@/lib/accounting/state"
+
+// Starts the OAuth connect flow for an accounting provider (owner-only).
+export async function GET(request: Request, { params }: { params: Promise<{ provider: string }> }) {
+  const { provider: pid } = await params
+  const prov = getProvider(pid)
+  const settings = new URL("/settings/integrations", request.url)
+
+  if (!prov) {
+    settings.searchParams.set("error", "unknown_provider")
+    return NextResponse.redirect(settings)
+  }
+
+  const user = await getSessionUser()
+  if (!user) return NextResponse.redirect(new URL("/login", request.url))
+
+  const ctx = await getAccountContext(user.id)
+  if (!ctx.isOwner) {
+    settings.searchParams.set("error", "owner_only")
+    return NextResponse.redirect(settings)
+  }
+  if (!prov.configured()) {
+    settings.searchParams.set("error", "not_configured")
+    return NextResponse.redirect(settings)
+  }
+
+  const state = signState({ ownerId: ctx.ownerId, provider: pid })
+  return NextResponse.redirect(prov.getAuthUrl(state))
+}