refactor(auth): rename paymentBridge → signupBridge

After commit 90acc35 issued the cookie for $0 signups too, the "payment"
framing was wrong — there's no payment in a $0 signup. The cookie is
about bridging the gap between signup-form submit and email verify, not
about payment specifically.

Changes:
- setPaymentBridgeCookie  → setSignupBridgeCookie
- getPaymentBridgeMember  → getSignupBridgeMember
- Cookie wire name        payment-bridge → signup-bridge
- JWT scope               payment_bridge → signup_bridge

Touches both /api/helcim/subscription (signup activation) and
/api/helcim/initialize-payment (paid Helcim checkout) which both consume
the cookie. In-flight signup sessions started before this lands will
need to re-submit the form (cookie name mismatch); cutover hasn't
happened yet, so the only impact is local dev sessions.

server/api/helcim/customer.post.js

@@ -4,7 +4,7 @@ import { connectDB } from '../../utils/mongoose.js'
 import { createHelcimCustomer } from '../../utils/helcim.js'
 import PreRegistration from '../../models/preRegistration.js'
 import { sendMagicLink } from '../../utils/magicLink.js'
-import { setPaymentBridgeCookie } from '../../utils/auth.js'
+import { setSignupBridgeCookie } from '../../utils/auth.js'
 import { rateLimit } from '../../utils/rateLimit.js'
 
 export default defineEventHandler(async (event) => {
@@ -116,10 +116,10 @@ export default defineEventHandler(async (event) => {
     })
 
     // Signup completes (paid checkout or free activation) before the magic
-    // link is clicked, so issue a short-lived, payment-only bridge cookie
-    // that lets /api/helcim/initialize-payment and /api/helcim/subscription
-    // identify the member without a verified auth session.
-    setPaymentBridgeCookie(event, member)
+    // link is clicked, so issue a short-lived signup-bridge cookie that lets
+    // /api/helcim/initialize-payment and /api/helcim/subscription identify
+    // the member without a verified auth session.
+    setSignupBridgeCookie(event, member)
 
     return {
       success: true,

server/api/helcim/initialize-payment.post.js

@@ -2,7 +2,7 @@ import Member from '../../models/member.js'
 import { loadPublicEvent } from '../../utils/loadEvent.js'
 import { loadPublicSeries } from '../../utils/loadSeries.js'
 import { calculateTicketPrice, calculateSeriesTicketPrice, hasMemberAccess } from '../../utils/tickets.js'
-import { requireAuth, getOptionalMember, getPaymentBridgeMember } from '../../utils/auth.js'
+import { requireAuth, getOptionalMember, getSignupBridgeMember } from '../../utils/auth.js'
 import { initializeHelcimPaySession } from '../../utils/helcim.js'
 
 export default defineEventHandler(async (event) => {
@@ -17,7 +17,7 @@ export default defineEventHandler(async (event) => {
 
     if (!isTicket) {
       if (isMembershipSignup) {
-        const bridgeMember = await getPaymentBridgeMember(event)
+        const bridgeMember = await getSignupBridgeMember(event)
         if (!bridgeMember) {
           await requireAuth(event)
         }

server/api/helcim/subscription.post.js

@@ -3,7 +3,7 @@ import { getHelcimPlanId, requiresPayment } from '../../config/contributions.js'
 import Member from '../../models/member.js'
 import { connectDB } from '../../utils/mongoose.js'
 import { getSlackService } from '../../utils/slack.ts'
-import { requireAuth, getPaymentBridgeMember } from '../../utils/auth.js'
+import { requireAuth, getSignupBridgeMember } from '../../utils/auth.js'
 import { createHelcimSubscription, generateIdempotencyKey, listHelcimCustomerTransactions } from '../../utils/helcim.js'
 import { sendWelcomeEmail } from '../../utils/resend.js'
 import { upsertPaymentFromHelcim } from '../../utils/payments.js'
@@ -11,8 +11,8 @@ import { upsertPaymentFromHelcim } from '../../utils/payments.js'
 export default defineEventHandler(async (event) => {
   try {
     // Membership signup completes subscription before email verify; allow the
-    // payment-bridge cookie set by /api/helcim/customer to satisfy auth here.
-    const bridgeMember = await getPaymentBridgeMember(event)
+    // signup-bridge cookie set by /api/helcim/customer to satisfy auth here.
+    const bridgeMember = await getSignupBridgeMember(event)
     if (!bridgeMember) {
       await requireAuth(event)
     }

server/utils/auth.js

@@ -23,26 +23,27 @@ export function setAuthCookie(event, member) {
 }
 
 /**
- * Issue a 30-minute payment-bridge cookie scoped to membership-signup checkout.
+ * Issue a 30-minute signup-bridge cookie scoped to membership-signup flow.
  *
  * The signup flow (POST /api/helcim/customer) defers the full session cookie
- * to email-verify (magic link). For paid tiers the user still needs to complete
- * Helcim checkout in the same browser tab — this short-lived, payment-only
- * token lets `/api/helcim/initialize-payment` accept the call without a full
- * session. The cookie is NOT honored by requireAuth and grants nothing else.
+ * to email-verify (magic link). The bridge cookie lets the in-progress signup
+ * complete its activation step (free or paid) before that magic link is
+ * clicked: /api/helcim/subscription accepts it for $0 activation, and
+ * /api/helcim/initialize-payment accepts it for paid Helcim checkout.
+ * The cookie is NOT honored by requireAuth and grants nothing else.
  */
-export function setPaymentBridgeCookie(event, member) {
+export function setSignupBridgeCookie(event, member) {
   const token = jwt.sign(
     {
       memberId: member._id.toString(),
       email: member.email,
-      scope: 'payment_bridge'
+      scope: 'signup_bridge'
     },
     useRuntimeConfig(event).jwtSecret,
     { expiresIn: '30m' }
   )
 
-  setCookie(event, 'payment-bridge', token, {
+  setCookie(event, 'signup-bridge', token, {
     httpOnly: true,
     secure: process.env.NODE_ENV === 'production',
     sameSite: 'lax',
@@ -52,12 +53,12 @@ export function setPaymentBridgeCookie(event, member) {
 }
 
 /**
- * Verify a payment-bridge cookie and return the associated Member, or null.
- * Used by /api/helcim/initialize-payment to allow the membership-signup
- * checkout to proceed before email verification.
+ * Verify a signup-bridge cookie and return the associated Member, or null.
+ * Used by /api/helcim/subscription and /api/helcim/initialize-payment to
+ * let the in-progress signup complete activation before email verification.
  */
-export async function getPaymentBridgeMember(event) {
-  const token = getCookie(event, 'payment-bridge')
+export async function getSignupBridgeMember(event) {
+  const token = getCookie(event, 'signup-bridge')
   if (!token) return null
 
   let decoded
@@ -67,7 +68,7 @@ export async function getPaymentBridgeMember(event) {
     return null
   }
 
-  if (decoded.scope !== 'payment_bridge') return null
+  if (decoded.scope !== 'signup_bridge') return null
 
   await connectDB()
   const member = await Member.findById(decoded.memberId)