DC-006: Add integration test for TOTP auth flow

Covers the full BACKLOG DC-006 acceptance criteria:
- GET /api/totp/config — read current config
- POST /api/totp/setup — generate / import Base32 secret
- POST /api/totp/verify-setup — activate TOTP after setup
- POST /api/totp/verify — login with TOTP code → session + CSRF
- GET /api/totp/check-session — auth gate (200 / 401)
- POST /api/totp/disable — disable TOTP (requires valid code)
- POST /api/totp/config — update session duration

25 tests, all passing. Uses real otplib for code generation
(so we exercise actual TOTP math) but mocks credentialManager,
session, totpConfig, saveTotpConfig — those own their own state
machines (disk, cookies, file) that don't belong in a routes
test.

Also fixed a latent DC-005 bug: routes/auth/totp.js had wrong
require-path depth after the refactor (../../../src/... went 3
levels up instead of 2, breaking route load). Changed to
../../src/... for the 2-level depth. NOTE: the same depth bug
exists in many other depth-2 route files (auth/keys.js,
auth/sso-gate.js, auth/session-handlers.js, recipes/*, apps/*,
arr/*, config/*) — see BACKLOG.md DC-005 follow-up note. Tests
didn't catch this because no test previously imported the auth
routes; this new test exercises that import path.

Result: 904/904 Jest tests pass (879 baseline + 25 new).
ESLint: this file clean. Pre-existing 134 src/ warnings are
unrelated (DC-005 refactor moved files without re-applying
DC-004 lint cleanup — separate follow-up).

dashcaddy-api/routes/auth/totp.js

@@ -1,6 +1,6 @@
 const express = require('express');
-const { ValidationError, AuthenticationError } = require('../../../src/utilities/errors');
-const { ok, successMessage } = require('../src/utils/responses');
+const { ValidationError, AuthenticationError } = require('../../src/utilities/errors');
+const { ok, successMessage } = require('../../src/utils/responses');
 
 /**
  * Auth TOTP routes factory