Implement Firebase Storage listing and byte-level progress observation: add async list/maxResults/pageToken and listAll on StorageReference, introduce StorageListResult wrapper (items, prefixes, pageToken), and add StorageTaskStatus/StorageProgress/StorageTaskSnapshot types. Implement observe/removeObserver/removeAllObservers for UploadTask and FileDownloadTask (with internal observer tracking) and provide no-op/overrides for other download tasks. Update tests to exercise list APIs and observer types, and update README to reflect increased Storage support; remove related TODO comments.

Clamp Int64 maxResults to the Swift Int range before casting to Int to prevent overflow when calling platformValue.list(...). Adds a `clamped` variable and uses it in both list(maxResults:) overloads so large or small Int64 values won't cause invalid Int conversion.