yattee-server returns direct YouTube CDN URLs in the storyboard `url`
and `templateUrl` fields instead of an Invidious-style VTT proxy path.
Two resulting issues:
- `Storyboard.directSheetURL` was replacing the whole `M$M` token with
just the index, producing `.../0.jpg` (404) instead of `.../M0.jpg`.
Replace `M$M` with `M\(index)` to preserve the literal `M` prefix;
matching the full token also avoids clobbering `$M` sequences that
may appear in `sigh=rs$...` query params.
- The download code fetched `proxyUrl` as if it were a WebVTT file;
with yattee-server that downloads a JPEG that fails UTF-8 parsing.
Skip the VTT round-trip when `proxyUrl` obviously points at an image.
Also align the on-disk filename with the local-playback template
(`sb_M$M.jpg` → `sb_M{N}.jpg`) so offline seek-bar previews resolve,
and add [Storyboard] debug logs at each decision point so future
failures can be diagnosed without guessing.
- Fix BGTaskScheduler assertion crash on Mac Catalyst by guarding all
iOS background task APIs with isMacCatalystApp check
- Fix iPad popover crash in UIPopoverPresentationController by adding
.presentationCompactAdaptation(.sheet) to all 27 confirmationDialogs
- Fix SwiftData assertion crash when accessing deleted Bookmark model
properties during SwiftUI hit testing in BookmarkRowView
- Fix UICollectionView invalid item count crash on queue swipe-to-delete
by using ID-based removal with withAnimation instead of stale index
- Fix Range crash in storyboard download when storyboardCount is zero
