fix: log errors from expired session cleanup and token usage tracking

internal/auth/service.go

@@ -109,7 +109,15 @@ func (s *authService) ValidateSession(ctx context.Context, sessionID string) (*d
 	}
 
 	if session.ExpiresAt.Before(time.Now()) {
-		_ = s.repo.DeleteSession(ctx, sessionID)
+		if err := s.repo.DeleteSession(ctx, sessionID); err != nil {
+			observability.Warn(
+				"delete_expired_session_failed",
+				"auth",
+				"",
+				map[string]any{"session_id": sessionID},
+				err,
+			)
+		}
 		return nil, errors.New("session expired")
 	}
 
@@ -141,7 +149,15 @@ func (s *authService) ValidateAPIToken(ctx context.Context, token string) (*doma
 		return nil, errors.New("token not found")
 	}
 
-	_ = s.repo.TouchAPITokenLastUsedAt(ctx, t.ID)
+	if err := s.repo.TouchAPITokenLastUsedAt(ctx, t.ID); err != nil {
+		observability.Warn(
+			"touch_api_token_last_used_at_failed",
+			"auth",
+			"",
+			map[string]any{"token_id": t.ID},
+			err,
+		)
+	}
 	return s.repo.GetUserByID(ctx, t.UserID)
 }