Zupt v2.1.2: add full-disk backup/restore, expand test suite, improve compression handling

- Introduced full-disk backup/restore (src/zupt_disk.c, ~530 LOC)
  - Backup: streams 4MB blocks with sparse detection and all codecs
  - Restore: per-block checksum validation for integrity
  - Supports password (-p), PQ hybrid (--pq), or no encryption
  - Real-time progress bar with throughput reporting (stderr)

- Implemented sparse detection (8-byte zero scan)
  - Zero blocks stored as STORE (near-zero overhead)

- Added disk-aware safeguards
  - ZUPT_FLAG_DISK_IMAGE prevents misuse with extract
  - Immediate failure on wrong password during first block decrypt

- Cross-platform device size detection
  - Linux: BLKGETSIZE64
  - macOS: DKIOCGETBLOCKCOUNT
  - Fallback: lseek

- Compression behavior
  - ~2928:1 on highly repetitive data
  - ~1.33:1 on random data (auto STORE fallback)

- Expanded test suite to 77 tests:
  - 11 VV unit
  - 13 NIST/RFC vectors
  - 22 regression
  - 14 multi-threaded
  - 10 post-quantum
  - 7 disk (normal, encrypted, PQ, sparse, LZHP, extreme compression, wrong-password)

Release stats:
- 74 files, 168KB, zero .o artifacts
- 77/77 tests passing
- Fully clean under ASAN + UBSan

ROADMAP.md

@@ -20,7 +20,8 @@
 | **v1.5.5** | **✅** | **Man page install, V=1 verbose, LDFLAGS/PIE, rpmlint, multi-arch Makefile** |
 | **v2.0** | **✅** | **VaptVupt 1.1.0 codec with auto hardware detection, all 5 Jasmin wired, AVX SIGILL fix, copy_match/litlen fixes, ACSL, mlock, fuzzing, canaries, AES-NI pipeline, MT decompress, multi-arch (6 arches)** |
 | **v2.1** | **✅** | **VaptVupt 1.4.0: cross-block dictionary, context prefetch, faster adaptive window, integration API** |
-| **v2.1.1** | **✅ Current** | **Termux/Android build fix, arch-safety guard, Keccak UB fix, no stale .o in tarballs** |
+| **v2.1.1** | **✅** | **Termux/Android build fix, arch-safety guard, Keccak UB fix, no stale .o in tarballs** |
+| **v2.1.2** | **✅ Current** | **Full-disk backup/restore with sparse detection, all encryption modes, progress bar, 77 tests** |
 
 ## Planned