chore(board): remove old board tests, update seed + onboarding tests

tests/server/api/onboarding-track.test.js

@@ -1,5 +1,13 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest'
 
+const { mockBoardPostExists } = vi.hoisted(() => ({
+  mockBoardPostExists: vi.fn()
+}))
+
+vi.mock('../../../server/models/boardPost.js', () => ({
+  default: { exists: mockBoardPostExists }
+}))
+
 vi.mock('../../../server/utils/auth.js', () => ({
   requireAuth: vi.fn()
 }))
@@ -45,6 +53,7 @@ describe('POST /api/onboarding/track', () => {
     })
     Member.findByIdAndUpdate.mockResolvedValue({})
     Member.findOneAndUpdate.mockResolvedValue(null) // no graduation by default
+    mockBoardPostExists.mockResolvedValue({ _id: 'post-1' })
   })
 
   // 2.1: Sets eventPageVisited to true