- Add shlex.quote() on all path arguments before subprocess calls (lines 404-407)
- Consolidate duplicated version_compare() function into single module-level utility
- Remove three identical class methods from UpdateCheckThread, LocalPendingUpdateCheckThread, and UpdateManager
- Add comprehensive test suite for updater.py security-critical functionality
- Add requirements-dev.txt with pytest dependency
Addresses critical security findings from flares_audit_report.md:
S001: Command Injection in Updater (CVSS ~7.5)
Q001: Duplicated version_compare logic
T001: Insufficient test coverage for updater.py
