Refactor snapshot dir creation to use secure permissions

Replaced `fs::create_dir_all` with `crate::paths::create_secure_dir_all` in `src/commands/snapshot.rs` to ensure the snapshot directory is created with secure default permissions (0o700) instead of relying on the system's default umask.

Co-authored-by: bitcoiner-dev <75873427+bitcoiner-dev@users.noreply.github.com>

Author: google-labs-jules[bot]

src/commands/snapshot.rs

@@ -7,7 +7,7 @@ use std::fs;
 pub async fn run(cli: &Cli, args: &SnapshotArgs) -> Result<CommandOutput, AppError> {
     let profile_path = profile_path(cli)?;
     let snap_dir = snapshot_dir(cli)?;
-    fs::create_dir_all(&snap_dir)
+    crate::paths::create_secure_dir_all(&snap_dir)
         .map_err(|e| AppError::Config(format!("failed to create snapshot dir: {e}")))?;
 
     match &args.action {