Backup & Restore Documentation Doesn't Mention Files

**OS & Hardware**
Linux

**Version**
1.10.3

**Describe the bug**
The [Backup & Restore | Dawarich](https://dawarich.app/docs/self-hosting/maintenance/backup-and-restore/) documentation talks about backing up the PostgreSQL database but I notice that my installation also has files in `/var/lib/dawarich/`. Notably I have the following files:

- `[12]/[23]/123456....` hex file names.
- `secrets/secret-key-base`
- `imports/watched`

These directories aren't mentioned in the docs at all which leads to concern. One would hope that these are ephemeral and that is why they aren't backed up but if so an explicit callout would make the reader far more confident in this case.

**To Reproduce**
Steps to reproduce the behavior:
1. Read https://dawarich.app/docs/self-hosting/maintenance/backup-and-restore/

**Expected behavior**
The user is correctly and confidently backing up their instance.

Start with the linked Backup & Restore documentation and inspect how the installation uses /var/lib/dawarich/, especially the listed hex files, secrets/secret-key-base, and imports/watched paths. Confirm which paths require backup or are ephemeral, then update the page so users can identify the complete backup requirements and verify the documented guidance.

Written by the indexing model from the issue text.