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>