Investigate account-guard test failure for nonexistent accounts #32

The full test suite fails in src/account/account.guard.spec.ts:130, in “should not be able to proceed with non-existing user.”

• Expected error message: Account does not exists
• Actual error message: Unauthorized
• Authentication is rejected; no authorization bypass was observed.
• The guard and test are unchanged by PR Fix TripNotify sharing, trip lists, and live updates #31. The underlying cause has not yet been diagnosed.

Reproduction

With dependencies installed and an isolated MongoDB database available:

DATABASE_URI=<test-database-uri> npm test -- --runInBand

Observed at commit a255fc7935c3017dcde3a2ea3a7fc04e69fb7fce using Node.js v22.23.2: 13 suites pass; the account-guard suite fails.

FAIL src/account/account.guard.spec.ts

  ● Test suite failed to run

    expect(received).rejects.toThrowError(expected)

    Expected substring: "Account does not exists"
    Received message:   "Unauthorized"

Acceptance criteria

• Diagnose the message mismatch and establish the expected error contract.
• Correct the implementation or test accordingly.
• Await asynchronous rejection assertions so failures are attributed correctly.
• Verify nonexistent accounts and invalid tokens remain rejected.

References

• PR #31 validation notes
• Failing test
• Guard error handling
• Implementation plan acknowledgement