refactor: return CataloggerError as Results instead of throwing in commands

Catalogger.Backend/CataloggerError.cs

@@ -13,6 +13,13 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
+using Remora.Results;
+using RemoraResult = Remora.Results.Result;
+
 namespace Catalogger.Backend;
 
-public class CataloggerError(string message) : Exception(message) { }
+public class CataloggerError(string message) : Exception(message), IResultError
+{
+    public static RemoraResult Result(string message) =>
+        RemoraResult.FromError(new CataloggerError(message));
+}