🛡️ Sentinel: [MEDIUM] Fix insecure snapshot directory permissions

[bitcoiner-dev]

🚨 Severity: MEDIUM
💡 Vulnerability: The snapshot directory was being created using the standard fs::create_dir_all function, which relies on the system's default umask (often 0755 or 022). This could potentially expose sensitive snapshot data or configuration to other users on the system if they have access to the data directory.
🎯 Impact: If a malicious local user gains access to the snapshot directory created with overly permissive permissions, they could potentially read sensitive wallet snapshot data.
🔧 Fix: Replaced fs::create_dir_all with crate::paths::create_secure_dir_all to enforce strict permissions (e.g., 0700 on Unix systems) when creating the snapshot directory, following defense-in-depth security best practices.
✅ Verification: Verified by checking that src/commands/snapshot.rs uses the create_secure_dir_all helper function. Ran cargo test and cargo clippy to ensure no regressions.

---

PR created automatically by Jules for task 18051328316366071199 started by @bitcoiner-dev

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.