fix(helcim): read dateBilling on subscription CREATE to populate next-billing cache

Helcim returns next-charge as `dateBilling` on POST /subscriptions, but the
two CREATE sites were reading `subscription.nextBillingDate`, leaving
`member.nextBillingDate` empty after every signup and free→paid upgrade.
The lazy refresh in subscription.get.js (which already accepts both shapes)
masked it on next account-page load, so renders eventually populated — but
the success response we returned to the client also had `nextBillingDate:
undefined`. Mirror the GET-side resolution at both CREATE sites: prefer
`dateBilling`, fall back to `nextBillingDate`. Existing Number.isNaN guard
unchanged; defensively rejects malformed strings from either field.

docs/LAUNCH_READINESS.md

@@ -142,7 +142,6 @@ See `docs/TODO.md` for:
 
 ### Known gotchas worth addressing post-launch
 
-- **Subscription cache fed wrong field on CREATE.** `subscription.post.js` and `update-contribution.post.js` read `subscription.nextBillingDate` from Helcim's CREATE response, but Helcim returns `dateBilling`. The lazy refresh in `subscription.get.js` masks this (handles both shapes), so next-charge rendering works — but the cache starts empty. Fix at the CREATE sites so the cache is correct from first write.
 - **Admin edit does not sync Helcim `recurringAmount`.** `/admin/members/[id]` PUT writes `contributionAmount` direct to Mongo by design. Admins must PATCH Helcim manually. Worth surfacing in admin UI or docs.
 - **Cadence switch rejected on active subscriptions.** `update-contribution.post.js:184-189` refuses cadence changes mid-subscription; no UI toggle exists on `/member/account`. Adding cadence switch would require a Helcim subscription replacement flow, not a plain update.
 - **`SeriesPassPurchase.vue` doesn't auto-refresh after purchase.** (Observed 2026-04-21 during Phase 4 series-pass functional tests.) Component's local `$fetch` to `/api/series/{id}/tickets/available` fires on mount + `userEmail` watch, but isn't re-invoked after a successful purchase — the "already registered" state only appears on next navigation. Parent page calls `refreshNuxtData()` but the component doesn't participate in it. Fix: call `fetchPassInfo()` after the success toast in `handleSubmit`, or lift the fetch to `useAsyncData` so it can be refreshed from outside.

server/api/helcim/subscription.post.js

@@ -167,9 +167,8 @@ export default defineEventHandler(async (event) => {
       throw createError({ statusCode: 500, statusMessage: 'Subscription creation failed' })
     }
 
-    const nextBillingDate = subscription.nextBillingDate
-      ? new Date(subscription.nextBillingDate)
-      : null
+    const rawNextBilling = subscription.dateBilling || subscription.nextBillingDate || null
+    const nextBillingDate = rawNextBilling ? new Date(rawNextBilling) : null
 
     // Atomically capture pre-update status alongside the write so we can
     // detect the pending_payment → active transition without a separate read
@@ -216,7 +215,7 @@ export default defineEventHandler(async (event) => {
       subscription: {
         subscriptionId: subscription.id,
         status: subscription.status,
-        nextBillingDate: subscription.nextBillingDate
+        nextBillingDate: rawNextBilling
       },
       member: {
         id: member._id,

server/api/members/update-contribution.post.js

@@ -100,9 +100,8 @@ export default defineEventHandler(async (event) => {
           throw new Error("No subscription returned in response");
         }
 
-        const nextBillingDate = subscription.nextBillingDate
-          ? new Date(subscription.nextBillingDate)
-          : null;
+        const rawNextBilling = subscription.dateBilling || subscription.nextBillingDate || null;
+        const nextBillingDate = rawNextBilling ? new Date(rawNextBilling) : null;
 
         // Update member record
         await Member.findByIdAndUpdate(
@@ -149,7 +148,7 @@ export default defineEventHandler(async (event) => {
           subscription: {
             subscriptionId: subscription.id,
             status: subscription.status,
-            nextBillingDate: subscription.nextBillingDate,
+            nextBillingDate: rawNextBilling,
           },
         };
       } catch (error) {

tests/server/api/helcim-subscription.test.js

@@ -166,6 +166,41 @@ describe('helcim subscription endpoint', () => {
     expect(Member.findById).toHaveBeenCalledWith('member-2')
   })
 
+  it('reads dateBilling from Helcim CREATE response and threads it to $set + response', async () => {
+    requireAuth.mockResolvedValue(undefined)
+    requiresPayment.mockReturnValue(true)
+    getHelcimPlanId.mockReturnValue('99999')
+
+    const mockMember = {
+      _id: 'member-db',
+      email: 'datebilling@example.com',
+      name: 'DateBilling User',
+      circle: 'founder',
+      contributionAmount: 15,
+      status: 'active',
+    }
+    Member.findOneAndUpdate.mockResolvedValue({ _id: 'member-db', status: 'pending_payment' })
+    Member.findById.mockResolvedValue(mockMember)
+    createHelcimSubscription.mockResolvedValue({
+      data: [{ id: 'sub-x', status: 'active', dateBilling: '2026-06-01' }]
+    })
+
+    const event = createMockEvent({
+      method: 'POST',
+      path: '/api/helcim/subscription',
+      body: { customerId: 'cust-1', contributionAmount: 15, customerCode: 'code-1', cardToken: 'tok-123', cadence: 'monthly' }
+    })
+
+    const result = await subscriptionHandler(event)
+
+    expect(Member.findOneAndUpdate).toHaveBeenCalledWith(
+      { helcimCustomerId: 'cust-1' },
+      { $set: expect.objectContaining({ nextBillingDate: new Date('2026-06-01') }) },
+      { new: false, runValidators: false, projection: { status: 1 } }
+    )
+    expect(result.subscription.nextBillingDate).toBe('2026-06-01')
+  })
+
   it('annual $15 tier creates subscription with correct paymentPlanId and recurringAmount', async () => {
     requireAuth.mockResolvedValue(undefined)
     requiresPayment.mockReturnValue(true)

tests/server/api/update-contribution.test.js

@@ -261,6 +261,30 @@ describe('update-contribution endpoint — Case 1 (free→paid)', () => {
     expect(result.message).toBe('Successfully upgraded to paid tier')
   })
 
+  it('reads dateBilling from Helcim CREATE response and threads it to $set + response', async () => {
+    setMember(freeMember)
+    getHelcimPlanId.mockReturnValue('111')
+    getHelcimCustomer.mockResolvedValue({ customerCode: 'code-1' })
+    listHelcimCustomerCards.mockResolvedValue([{ id: 'card-1' }])
+    createHelcimSubscription.mockResolvedValue({ data: [{ id: 'sub-new', status: 'active', dateBilling: '2026-05-18' }] })
+    Member.findByIdAndUpdate.mockResolvedValue({})
+
+    const event = createMockEvent({
+      method: 'POST',
+      path: '/api/members/update-contribution',
+      body: { contributionAmount: 15, cadence: 'monthly' },
+    })
+
+    const result = await handler(event)
+
+    expect(Member.findByIdAndUpdate).toHaveBeenCalledWith(
+      'member-c1',
+      { $set: expect.objectContaining({ nextBillingDate: new Date('2026-05-18') }) },
+      { runValidators: false }
+    )
+    expect(result.subscription.nextBillingDate).toBe('2026-05-18')
+  })
+
   it('annual: calls createHelcimSubscription with annual plan id and recurringAmount 180, persists billingCadence annual', async () => {
     setMember(freeMember)
     getHelcimPlanId.mockReturnValue('222')