🛡️ Sentinel: [CRITICAL] Fix path traversal in profile paths

[bitcoiner-dev]

🚨 Severity: CRITICAL
💡 Vulnerability: config.profile was being used unvalidated in Path::join when constructing profile paths and snapshot directories. If config.profile contained string values like ../ or /absolute/path, Path::join would traverse the filesystem resulting in arbitrary file creation or manipulation under profiles/ and snapshots/.
🎯 Impact: This allows malicious profile strings to write data outside the designated directory structure, leading to potential data corruption or arbitrary file writes.
🔧 Fix: Added validate_file_name in src/utils.rs which implements a strict allowlist matching for alphanumeric characters, dashes, and underscores. Applied this validation inside src/paths.rs during path generation so any traversal character causes a safe exit via AppError::Invalid.
✅ Verification: Ensure the updated cargo test --bin zinc-cli passes completely and explicitly checks the new test blocks rejecting paths like ../invalid or /etc/passwd.

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PR created automatically by Jules for task 10536558652879364844 started by @bitcoiner-dev

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