feat(dedup): CDC sub-file deduplication with FastCDC + parallel chunk storage + dedup skip
- Replace whole-file SHA-256 dedup with FastCDC 2020 content-defined chunking
(min 64KB, avg 256KB, max 1MB) + BLAKE3 hashing
- Add chunk_manifests table (file_hash → chunk_hashes[] + chunk_sizes[])
- Add put_blob_from_bytes to BlobStorageBackend trait (all 7 backends)
- 3-phase store_chunks pipeline:
Phase 0: batch-check existing chunks (single PG query)
Phase 1: selective disk read (skip existing chunks entirely)
Phase 2: parallel upload with buffer_unordered(8)
- CDC-aware read_blob_stream and read_blob_range_stream with legacy fallback
- Transactional manifest + chunk ref-count cascade on remove_reference
- 12 CDC tests (determinism, reassembly, contiguity, sub-file dedup, etc.)
- Update deduplication.md to reflect new architecture
Diocrafts
761d159a92