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/stripe/checkout/route.ts

@@ -5,16 +5,26 @@ import { profiles } from "@/lib/db/schema"
 import { getSessionUser } from "@/lib/session"
 import { stripe } from "@/lib/stripe/client"
 import { PLAN_PRICES } from "@/lib/stripe/plans"
+import { resolvePriceId } from "@/lib/stripe/prices"
 
 export async function POST(request: Request) {
   const user = await getSessionUser()
   if (!user) return NextResponse.json({ error: "Unauthorized" }, { status: 401 })
 
-  const { plan } = await request.json() as { plan: string }
+  const { plan, interval } = await request.json() as {
+    plan: string
+    interval?: "month" | "year"
+  }
 
   const planConfig = PLAN_PRICES[plan]
   if (!planConfig) return NextResponse.json({ error: "Invalid plan" }, { status: 400 })
 
+  const billingInterval = interval === "year" ? "year" : "month"
+  const priceId = await resolvePriceId(planConfig.plan, billingInterval)
+  if (!priceId) {
+    return NextResponse.json({ error: "Could not resolve the plan price. Check STRIPE_SECRET_KEY." }, { status: 400 })
+  }
+
   const profile = await db.query.profiles.findFirst({
     where: eq(profiles.id, user.id),
     columns: { stripe_customer_id: true, email: true, full_name: true },
@@ -27,7 +37,7 @@ export async function POST(request: Request) {
     const customer = await stripe.customers.create({
       email: profile?.email ?? user.email,
       name: profile?.full_name ?? undefined,
-      metadata: { supabase_user_id: user.id },
+      metadata: { user_id: user.id },
     })
     customerId = customer.id
 
@@ -43,16 +53,16 @@ export async function POST(request: Request) {
   const session = await stripe.checkout.sessions.create({
     customer: customerId,
     mode: isLifetime ? "payment" : "subscription",
-    line_items: [{ price: planConfig.priceId, quantity: 1 }],
+    line_items: [{ price: priceId, quantity: 1 }],
     success_url: `${appUrl}/settings/billing?success=true`,
     cancel_url: `${appUrl}/settings/billing?canceled=true`,
     metadata: {
-      supabase_user_id: user.id,
+      user_id: user.id,
       plan: planConfig.plan,
     },
     ...(isLifetime ? {} : {
       subscription_data: {
-        metadata: { supabase_user_id: user.id, plan: planConfig.plan },
+        metadata: { user_id: user.id, plan: planConfig.plan },
       },
     }),
   })