fix(dedup): use deterministic seed in TestChunker_ShiftedData

The test was flaky because it used crypto/rand for random data,
causing non-deterministic chunk boundaries. With small sample sizes
(100KB / 8KB avg = ~12 chunks), variance was high - sometimes only
42.9% overlap instead of expected >50%.

Fixed by using math/rand with seed 42 for reproducible test results.
Now consistently achieves 91.7% overlap (11/12 chunks).

bin/README.md

@@ -3,9 +3,9 @@
 This directory contains pre-compiled binaries for the DB Backup Tool across multiple platforms and architectures.
 
 ## Build Information
-- **Version**: 3.42.49
-- **Build Time**: 2026-01-16_14:37:18_UTC
-- **Git Commit**: bfe99e9
+- **Version**: 3.42.50
+- **Build Time**: 2026-01-16_14:53:54_UTC
+- **Git Commit**: 5728b46
 
 ## Recent Updates (v1.1.0)
 - ✅ Fixed TUI progress display with line-by-line output