1.5.4 — Managed support adverts

Adds visible CryptoLabs managed support adverts to the Fleet login screen and landing page. Both link to https://cryptolabs.co.za, and the dashboard footer includes an explicit support link.

Verified with 930 regression tests passing (2 existing skips), focused login/setup/error-state tests, desktop/mobile previews, independent code review, and required release builds.