Managed mode: keep the admin settings and addons ratchets green

- The phone's OIDC card moves into MAdminOidcCard, so the settings section
  is back within its complexity limit after the managed-mode conditions.
- enabledPhotoProviderIds reads the enabled ids straight from the
  repository and has a test of its own, which brings the addons coverage
  back to its threshold.

server/src/nest/addons/addons.service.ts

@@ -117,7 +117,7 @@ export class AddonsService {
   /** The photo providers users can connect: none while the journey addon is off. */
   async enabledPhotoProviderIds(): Promise<string[]> {
     if (!(await this.isAddonEnabled(ADDON_IDS.JOURNEY))) return [];
-    return (await this.photoProviders.listEnabled()).flatMap((row) => (row.id ? [row.id] : []));
+    return this.photoProviders.listEnabledIds();
   }
 
   /** wanderer may be used: Tours is on and the admin allowed it under Tours. */