feat: Encrypt session keys with SSH key for improved security

[jahwag]

Pull Request Description

This PR enhances the security of the system by encrypting session keys using an SSH key. With this change, session keys are no longer stored in plaintext, making them more secure and resistant to unauthorized access.

By encrypting session keys with an SSH key, the system also becomes ready for securely storing other sensitive credentials, such as API keys, in the future.

Checklist

• Changes are limited to a single goal (avoid scope creep)
• I confirm that I have read any Contribution and Development guidelines (CONTRIBUTING and DEVELOPMENT) and are following their suggestions.
• I confirm that I wrote and/or have the right to submit the contents of my Pull Request, by agreeing to the Developer Certificate of Origin, (adding a 'sign-off' to my commits).

[sabeer-narula]

Would you be able to add a step in the directions about needing an RSA SSH key on your device in order to get claudesync to work now? I added it to my new project and it took me a while to figure out why I couldn't set it up on my new project comapred to the one i was working on a week ago.