fix: validate HTTP status code in downloadTemplate to reject non-200 responses

[DevLikhith5]

Closes #370.

The Bug

downloadTemplate() pipes the HTTP response directly to a file without checking response.statusCode. A 404 or 500 is silently treated as a successful download.

The Fix

Added a status code check consistent with the pattern already used in downloadClientFromRelease and downloadTypesFromRelease (which were already fixed in an earlier commit):

if(response.statusCode !== 200) {
    file.close();
    reject(new Error(`Failed to download template: HTTP ${response.statusCode}`));
    return;
}

Checklist

• Conventional Commit (fix:)
• CHANGELOG updated
• No new dependencies
• No modern JS features