test(seed): add pending_payment persona for wave-slack §7.3

The §7.3 test referenced jennie@jenniefaber.com — the user's real
email, never seeded — so the test only worked locally on the
maintainer's machine. Add a generic 'pending-payment-test@example.test'
persona to seed-members.js and point the test at it.

scripts/seed-members.js

@@ -274,6 +274,18 @@ const sampleMembers = [
     createdAt: new Date('2025-06-01'),
     lastLogin: new Date('2026-04-04'),
   },
+  {
+    email: 'pending-payment-test@example.test',
+    name: 'Pending Payment Tester',
+    circle: 'community',
+    contributionAmount: 5,
+    status: 'pending_payment',
+    slackInvited: false,
+    craftTags: [],
+    board: {},
+    createdAt: new Date('2026-04-25'),
+    lastLogin: new Date('2026-04-29'),
+  },
 ]
 
 const TEST_ADMIN_BOARD = {