Switch to policy-based authorization for controllers

Replaced role-based [Authorize] attributes with policy-based ones in AuthController and TfaRegistrationController. This centralizes authorization logic and allows for more flexible access control.

EnvelopeGenerator.API/Controllers/TfaRegistrationController.cs

@@ -111,7 +111,7 @@ public class TfaRegistrationController : ControllerBase
     /// <summary>
     /// Logs out the envelope receiver from cookie authentication.
     /// </summary>
-    [Authorize(Roles = Role.FullyAuth)]
+    [Authorize(Policy = AuthorizationPolicies.ReceiverFullyAuth)]
     [HttpPost("auth/logout")]
     public async Task<IActionResult> LogOutAsync()
     {