🛡️ Sentinel: [CRITICAL] Fix Path Traversal in Snapshot Command

[bitcoiner-dev]

🚨 Severity: CRITICAL
💡 Vulnerability: Path traversal in the snapshot command via unvalidated name arguments passed directly to PathBuf::join. Standard directory creation via fs::create_dir_all could also have insecure default permissions.
🎯 Impact: An attacker could read from or write to unintended files/directories outside the standard profile directory using sequences like ../.
🔧 Fix: Added a new utility validate_file_name that restricts input to alphanumeric characters, dashes, and underscores. Enforced this validation on the name argument in the snapshot command. Replaced standard fs::create_dir_all with create_secure_dir_all to ensure secure permissions.
✅ Verification: Verified compilation and successfully passed the test suite locally. Evaluated secure pathing constraints using a simulated code review.

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PR created automatically by Jules for task 9740700310746200504 started by @bitcoiner-dev

[google-labs-jules]

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