v0.7.7

Release v0.7.7 - Security audit fixes

Security hardening release addressing audit findings:
- Fixed constant-time comparison test with realistic timing tolerance
- Added integer overflow validation for archive handlers
- Documented non-cryptographic RNG usage
- Verified all crypto operations use crypto/rand
- Validated zip-slip protection and race conditions
- All 109 tests passing with race detector clean

Security improvements:
- Enhanced documentation for security-critical code paths
- Safe integer conversion checks
- Comprehensive security audit report included