[Kimlimp]

Summary

• Bounded EPG orphan lookup: Eliminates unbounded fetch of all surviving channels across all other playlists.
• Fast-path for no-EPG playlists: Immediately skips guide orphan lookup when the removed playlist has no EPG channels.
• Keyset-paged candidate batches: Evaluates removed channels and surviving references in bounded batches (500 per page) inside an autoreleasepool, keeping resident memory strictly O(batchSize).
• Preserved shared guide listings: Only guide listings with zero surviving channel references are pruned.
• Bounded series cascade: Reduces Series deletion page size from 2,000 to 200, avoiding memory spikes when cascading to episodes.

Testing

• Added tests in PlaylistDeletionTests covering no-EPG playlists, multi-playlist shared guides, cloud reconcile entry point, single huge series (1,500 episodes), and multi-page channel batches.
• Verified all tests in PlaylistDeletionTests and CloudSyncDeletionTests pass on iOS 27.2 Simulator (iPhone 18 Pro).
• Passed swiftformat and swiftlint pre-commit checks.