NestJS Unit Testing with Jest: Mock PrismaService and Test JWT Auth e8

Everything we built last episode was verified by hand with Docker running. That does not scale, so this episode replaces all of it with a test suite that finishes in three seconds with nothing else started.

We wire Jest and ts-jest into the NestJS backend, build a testing module with Test.createTestingModule, swap PrismaService for a plain object made of jest.fn, and unit test the real AuthService.