refactor(secure.mdx): SSH Configuration and Fix Typos

[Pawel-itv]

Improving Documentation

• Run pnpm lint:fix to fix formatting issues before opening the PR.
• Read the Docs Contribution Guide: https://vitnode.com/docs/dev/contribution

Description

What?

• Refactoring SSH-related commands and instructions for enhanced clarity and to prevent potential login issues.
• Adding missing steps, such as setting the correct file permissions (chmod 600) for authorized_keys, ensuring secure SSH access.
• Correcting terminology by replacing incorrect references to SSL with SSH where applicable.
• Fixing typos and making general improvements to the documentation for better readability and accuracy.

Why?

The changes improve the reliability and security of SSH configuration by clarifying instructions, correcting terminology, and ensuring correct file permissions (chmod 600) for SSH keys.

How?

• Refactored and clarified SSH-related commands and documentation, ensuring accuracy.
• Added missing instructions for setting file permissions, including the use of chmod 600 on authorized_keys to secure SSH keys.
• Replaced incorrect SSL references with SSH where appropriate.
• Fixed typos and made other enhancements to improve the readability of the documentation.

[aXenDeveloper]

Thank you!