Improve documentation for optional password setup with step-by-step guidance

[Garima-149]

While exploring the documentation, I noticed that the optional password creation step is mentioned but not clearly explained for first-time users.

It is currently unclear:

• where exactly in the UI the password needs to be set
• at which stage of the setup process this option appears
• how enabling/disabling the password affects backup security

This may cause confusion, especially for beginners who are not familiar with Borg/Vorta concepts.

Proposed Improvements:

• Add clear step-by-step instructions for setting up the optional password
• Include screenshots highlighting the relevant UI sections
• Briefly explain the purpose and importance of setting a password

This would improve usability and help users make informed decisions about securing their backups.

I would like to work on this issue and submit a pull request.

OS : Windows

[Denay2468]

Hi! I'd like to work on this issue.

I noticed that Vorta's user-facing documentation lives on
vorta.borgbase.com which appears to be a separate repository.
Before I proceed, could the maintainers clarify:

1. Should the step-by-step instructions and screenshots be added
   to the vorta.borgbase.com docs repo, or is there a preferred
   location within this repo?

2. Would improving in-app guidance (tooltips, placeholder text)
   also be acceptable as part of this fix?

I have already made a small start by adding a tooltip to the
encryption combobox and clarifying the passphrase placeholder text,
but I want to make sure I'm working in the right direction before
submitting a full PR.

Thanks!