♻️ Refactor OpenID: Phase 3: Async Flow Modernization

- Added async GetAuthorizationUrlAsync() methods to all OIDC providers
- Updated base OidcService with abstract async contract and backward-compatible sync wrapper
- Modified OidcController to use async authorization URL generation
- Removed sync blocks using .GetAwaiter().GetResult() in Google provider
- Maintained backward compatibility with existing sync method calls
- Eliminated thread blocking and improved async flow throughout auth pipeline
- Enhanced scalability by allowing non-blocking async authorization URL generation

DysonNetwork.Pass/Auth/OpenId/DiscordOidcService.cs

@@ -16,6 +16,11 @@ public class DiscordOidcService(
     protected override string DiscoveryEndpoint => ""; // Discord doesn't have a standard OIDC discovery endpoint
     protected override string ConfigSectionName => "Discord";
 
+    public override Task<string> GetAuthorizationUrlAsync(string state, string nonce)
+    {
+        return Task.FromResult(GetAuthorizationUrl(state, nonce));
+    }
+
     public override string GetAuthorizationUrl(string state, string nonce)
     {
         var config = GetProviderConfig();
@@ -111,4 +116,4 @@ public class DiscordOidcService(
             Provider = ProviderName
         };
     }
-}
+}