Add support for SHA-384 hash algorithm

[sorooshm78]

Thanks for the great app. I needed SHA-384 support for my use case, which wasn’t available in Aegis, so I implemented it. Opening this PR so others can benefit as well.

[alexbakker]

We've previously closed #1679 because we couldn't find any services using SHA-384 for TOTP. Which service did you encounter that requires it?

[sorooshm78]

Hi @alexbakker,

Thanks for getting back to me. I encountered this requirement within our organization. We use a custom internal enterprise SSO and VPN gateway where the network administrators have specifically configured the TOTP generation to use SHA-384.

Regarding your second question, as far as I know, Google Authenticator does not support SHA-384. I only added ALGORITHM_SHA384 = 5 to google_auth.proto for the sake of completeness in the code.

I can completely revert the changes made to the .proto file (and related Google Auth migration code) and only keep the core SHA-384 implementation for Aegis itself. Let me know if you’d like me to update the PR!