feat: gravity transaction logging + user-facing history popup

- New GravityTransaction schema tracks all gravity changes (registration,
  interview/optimize/download deduction, purchase, monthly topup, migration)
- GravityTopUpService: bulk log for monthly VIP topup
- PaymentController.activateMembership: log plan_set transactions
- QuotaService: add logTransaction, wire into all gravity-modifying methods
- UserService: log registration grants (phone/wx/email/password)
- GET /user/gravity-transactions?page=&limit= API
- Frontend: user.vue '明细' button + paginated popup
- Docs: update PROJECT-STATUS v4.10, FEATURE-LIST, DEPLOYMENT

backend/src/modules/user/user.service.spec.ts

@@ -4,6 +4,7 @@ import { JwtService } from '@nestjs/jwt'
 import { HttpException } from '@nestjs/common'
 import { UserService } from './user.service'
 import { EmailService } from '../email/email.service'
+import { PricingService } from '../schemas/pricing.service'
 
 describe('UserService', () => {
   let service: UserService
@@ -44,8 +45,10 @@ describe('UserService', () => {
       providers: [
         UserService,
         { provide: getModelToken('User'), useValue: mockUserModel },
+        { provide: getModelToken('GravityTransaction'), useValue: { create: jest.fn() } },
         { provide: JwtService, useValue: mockJwtService },
         { provide: EmailService, useValue: mockEmailService },
+        { provide: PricingService, useValue: { getConfig: jest.fn().mockResolvedValue({ registrationGravity: 50, gravityRates: { interviewPerUse: 5, optimizePerUse: 3, downloadPerUse: 2 }, plans: { growth: { gravityPerMonth: 80 }, sprint: { gravityPerMonth: 200 } } }) } },
       ],
     }).compile()