Permission error when running in Docker

# Permission error when running in Docker

## Issue
When running in a Docker container, the module fails with permission errors when trying to write to the `.itemsBackup.json` file within the module's parent directory. This breaks in containerized environments with restricted permissions.

```
[3/26/2025, 20:05:27 UTC] Warning > [SKYHELPER-NETWORTH] Failed to retrieve items: Error: EACCES: permission denied, open '/usr/src/app/node_modules/skyhelper-networth/.itemsBackup.json'. Retrying (3 attempt(s) left)...
[3/26/2025, 20:05:28 UTC] Warning > [SKYHELPER-NETWORTH] Failed to retrieve items: Error: EACCES: permission denied, open '/usr/src/app/node_modules/skyhelper-networth/.itemsBackup.json'. Retrying (2 attempt(s) left)...
[3/26/2025, 20:05:29 UTC] Warning > [SKYHELPER-NETWORTH] Failed to retrieve items: Error: EACCES: permission denied, open '/usr/src/app/node_modules/skyhelper-networth/.itemsBackup.json'. Retrying (1 attempt(s) left)...
ItemsError: [SKYHELPER-NETWORTH] Failed to retrieve items: Error: EACCES: permission denied, open '/usr/src/app/node_modules/skyhelper-networth/.itemsBackup.json'.
at NetworthManager.updateItems (/usr/src/app/node_modules/skyhelper-networth/managers/NetworthManager.js:161:28)
at process.processTicksAndRejections (node:internal/process/task_queues:105:5)
at async NetworthManager.updateItems (/usr/src/app/node_modules/skyhelper-networth/managers/NetworthManager.js:165:20)
at async NetworthManager.updateItems (/usr/src/app/node_modules/skyhelper-networth/managers/NetworthManager.js:165:20)
at async NetworthManager.updateItems (/usr/src/app/node_modules/skyhelper-networth/managers/NetworthManager.js:165:20)
```

## Environment
- Container environment: Docker
- Node.js version: 22.14.0
- Module version: v2