chore(backend): add roslynator and fix diagnostics

Foxnouns.Backend/Services/Auth/RemoteAuthService.cs

@@ -142,6 +142,8 @@ public class RemoteAuthService(
             || accountState.UserId != userId
             || (instance != null && accountState.Instance != instance)
         )
+        {
             throw new ApiError.BadRequest("Invalid state", "state", state);
+        }
     }
 }

Foxnouns.Backend/Services/UserRendererService.cs

@@ -74,7 +74,9 @@ public class UserRendererService(
             user.Timezone != null
             && TimeZoneInfo.TryFindSystemTimeZoneById(user.Timezone, out TimeZoneInfo? tz)
         )
+        {
             utcOffset = (int)tz.GetUtcOffset(DateTimeOffset.UtcNow).TotalSeconds;
+        }
 
         return new UserResponse(
             user.Id,