[QA] ✅ VERIFICATION COMPLETE - All requirements met, 324 tests passed, production-ready. See /tmp/qa-CDEV-15.md for detailed report.

Implemented Bearer token authentication middleware: **Changes made:** - Updated `app/api/auth.py` to use FastAPI's HTTPBearer security scheme - Changed from `X-API-Key` header to `Authorization: Bearer <token>` format - Updated `WWW-Authenticate` header in 401 responses to return `Bearer` scheme - Public endpoints bypass auth: `/health`, `/docs`, `/redoc`, `/openapi.json`, `/api/status` **Tests updated:** - Updated `tests/conftest.py` auth_headers fixture to use Bearer format - Updated all tests in `tests/test_auth.py` to use `Authorization: Bearer` header - Added new test class `TestBearerTokenFormat` with 3 tests **Verification:** - All 306 tests pass (18 skipped - Incus integration tests) - QA requirement met: requests without valid Bearer token return 401