test(fxa-auth-server): migrate DB, Redis & storage tests from Mocha to Jest (FXA-12564)

- Convert DB, Redis, and storage test files from Mocha/Chai to Jest
- Set maxWorkers=4 for Jest unit tests to prevent OOM kills
- Use page.waitForURL for pairing flow success check in functional tests

Author: vbudhram

packages/fxa-auth-server/jest.config.js

@@ -21,6 +21,7 @@ module.exports = {
   },
   testTimeout: 10000,
   clearMocks: true,
+  maxWorkers: 4,
   workerIdleMemoryLimit: '512MB',
   setupFiles: ['<rootDir>/jest.setup.js', '<rootDir>/jest.setup-proxyquire.js'],
   testPathIgnorePatterns: ['/node_modules/'],