typub-storage 0.1.0

S3-compatible storage client, status tracking, and asset types for typub.

This crate provides:

• S3Storage — S3-compatible storage client
• UploadResult — result of an asset upload
• PendingAsset, PendingAssetList, DeferredAssets — deferred asset types
• StatusTracker — SQLite-backed publish status tracking
• Asset upload orchestration (materialize_external_assets, etc.)
• Pure utility functions for hash computation, URL construction, encoding, etc.

Extracted per [[RFC-0007:C-SHARED-TYPES]] to enable adapter subcrates to handle asset uploads without depending on the main crate.