Encrypt authentication credentials at rest

[shellcatt]

Description

Currently, authentication credentials are being stored via configstore in plain text inside the user's config directory.
This presents a security risk, and the credentials should be encrypted at rest and decrypted on demand.
A intermediate user-defined password/key/pin would be a good solution for now.

Acceptance Criteria:

• Authentication credentials must be encrypted before being saved to configstore.
• Decryption should occur when credentials are accessed.
• Ensure backward compatibility with existing configurations.
• Add tests to verify encryption and decryption functionality.