fix: handle object-format select_options from Paperless for Freigabe field

Paperless may return extra_data.select_options as an array of objects
{id, label} instead of plain strings. This caused React error #31
when Ant Design tried to render an object as a child in the Select and
Table components.

- Backend: coerce option items to {id: string, label: string} regardless
  of whether Paperless returns strings or objects
- Frontend: normalize cf.value to a plain string before rendering or
  storing in state, guarding against object-typed values

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

paperless-backend/src/freigabe/freigabe.service.ts

@@ -98,9 +98,19 @@ export class FreigabeService {
     const field = (fields as any[]).find((f: any) => f.id === FREIGABE_FIELD_ID);
     if (!field) return [];
 
-    const options: string[] = field.extra_data?.select_options ?? [];
-    return options
+    const rawOptions: any[] = field.extra_data?.select_options ?? [];
+    return rawOptions
       .filter((o) => o !== null && o !== undefined && o !== '')
-      .map((o) => ({ id: o, label: o }));
+      .map((o) => {
+        if (typeof o === 'object') {
+          // Paperless kann select_options als Objekte liefern
+          return {
+            id: String(o.id ?? o.value ?? o.label ?? ''),
+            label: String(o.label ?? o.name ?? o.id ?? ''),
+          };
+        }
+        return { id: String(o), label: String(o) };
+      })
+      .filter((o) => o.id !== '');
   }
 }