Wires MyPageController.Index to read Viewer.MyPageBgId/SelectType/BgRotation
instead of emitting an empty MyPageBgSetting placeholder; adds Include for
MyPageBgRotation in ViewerRepository.GetViewerByShortUdid; adds fresh-viewer
zero-defaults test and write→read round-trip test (9/9 controller tests pass).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Add a comment above MyPageBgRotation.Clear() explaining the EF OwnsMany
delete-on-clear semantics. Add a 7th test covering garbage/"" entries in
mypage_id_list falling back to BgId=0 while adjacent valid entries are
unaffected.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
