feat: add secure secret generation with 'secret_' prefix

[rosenbach]

This pull request introduces a cryptographically secure secret generation feature and provides a generate-button for the client id.

The main changes in this PR are:

• Replacing the previous GUID-based secret generation method with a more flexible and secure approach that generates a random byte array and converts it to a hexadecimal string.
• Adding a "secret_" prefix to the generated secret to provide better context and readability. This is recommended here: https://www.oauth.com/oauth2-servers/client-registration/client-id-secret/
• Renamed the Secrets.js class and methods to be more generic, as the updated code now handles both secret and client ID generation.
• Adding a generate-button to the Client ID field, similar to the Secret Input field

[skoruba]

Thank you, this looks nice, I am sorry for delay.