feat(registratie): WP-36 — admin cases page + admin delete

Admin-only overview of all cases across owners + an admin delete, gated by a new
`cases:manage` capability (Authz role→cap + CanManageCases + CasesAdmin gate;
FE capability + guard + nav + role.interceptor prefix — the org-template/stamdata
recipe). Backend adds ApplicationStore.ListAll()/DeleteAny() and GET /admin/cases +
DELETE /admin/cases/{id}; admin delete removes ANY case incl. submitted. Page lives
in registratie/ui (owns the Aanvraag aggregate; reuses aanvraag-view + parse),
routed /beheer/zaken; delete guarded by a native confirm, optimistic with rollback.
Typed client regenerated (documents the new endpoints + owner field).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/BigRegister.Api/Contracts/Mappers.cs

@@ -55,6 +55,10 @@ public static class Mappers
       a.Id, a.Type, a.ToStatusDto(now), a.DocumentIds,
       a.CreatedAt.ToString("o"), a.UpdatedAt.ToString("o"), a.SubmittedAt?.ToString("o"));
 
+  /// Admin summary — same shape plus the owner (WP-36; the user-facing list leaves Owner null).
+  public static ApplicationSummaryDto ToAdminSummaryDto(this Aanvraag a, DateTimeOffset now) =>
+      a.ToSummaryDto(now) with { Owner = a.Owner };
+
   public static ApplicationDetailDto ToDetailDto(this Aanvraag a, DateTimeOffset now) => new(
       a.Id, a.Type, a.ToStatusDto(now), a.Draft, a.DocumentIds,
       a.CreatedAt.ToString("o"), a.UpdatedAt.ToString("o"), a.SubmittedAt?.ToString("o"));