CompressStream had both a defer w.Close() and an explicit w.Close() call,
causing the compressor and encryptor to be closed twice. The second close
on the zstd encoder returns an error, and the age encryptor may write
duplicate finalization bytes, potentially corrupting the output stream.
Use a closed flag to prevent the deferred close from running after the
explicit close succeeds.
- Add unified compression/encryption package in internal/blobgen
- Update DATAMODEL.md to reflect current schema implementation
- Refactor snapshot cleanup into well-named methods for clarity
- Add snapshot_id to uploads table to track new blobs per snapshot
- Fix blob count reporting for incremental backups
- Add DeleteOrphaned method to BlobChunkRepository
- Fix cleanup order to respect foreign key constraints
- Update tests to reflect schema changes
