Regenerates media conversions.
This task is useful when you've changed conversion definitions and need to regenerate all derived images.
Usage
# Regenerate all conversions for all media
$ mix phx_media_library.regenerate
# Regenerate specific conversion
$ mix phx_media_library.regenerate --conversion thumb
# Regenerate for specific collection
$ mix phx_media_library.regenerate --collection images
# Regenerate for specific model type
$ mix phx_media_library.regenerate --model posts
# Dry run (show what would be regenerated)
$ mix phx_media_library.regenerate --dry-runOptions
--conversion Only regenerate this conversion (can be repeated)
--collection Only regenerate for this collection
--model Only regenerate for this model type (e.g., "posts")
--dry-run Show what would be regenerated without doing it
--batch-size Number of items to process at once (default: 100)