fix(onlyoffice/desktop-mobile): enforce iframe and nested iframe height after...

https://gitlab.e.foundation/e/infra/backlog/-/issues/4553

Fixes / Changes

- Hide recovery email banner when on OnlyOffice apps (/apps/onlyoffice or https://oo.*)
- Reset header positioning (top: 0) for clean layout without banner space
- Remove topHeight styling from all header elements (#header, #header-menu-*)
- Position main content below header instead of behind it
- Set main content height to 100% for proper OnlyOffice iframe display
- Monitor URL changes for SPA navigation to apply changes dynamically