fix: category bulk-delete had no confirmation, single-delete used native dialogs

Bulk-delete called facade.applyBulkDelete() straight from the button
with zero confirmation. Single-delete had a confirm gate but via raw
window.confirm/alert instead of the themed dialog used elsewhere.

Migrated both to app-confirm-dialog (single + new bulk), and the
delete-blocked message to a themed app-dialog instead of window.alert.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/i18n/en.ts

@@ -1549,6 +1549,8 @@ export const en: Translations = {
     saveDraft: 'Save draft',
     publish: 'Publish',
     confirmDelete: 'Delete this category? This cannot be undone.',
+    confirmBulkDelete: 'Delete the selected categories? This cannot be undone.',
+    deleteTitle: 'Delete category',
     confirmLeaveUnsaved: 'You have unsaved changes. Leave without saving?',
     deleteBlocked: 'This category can\'t be deleted while it has subcategories or assigned products.',
     emptyTitle: 'No categories yet',