refactor(delete): make undo unconditional, remove undo toggle and button delay

- Remove delete_undo_enabled setting (backend default, frontend state,
  settings modal UI, 10 locales); staged deletes with 30s undo are now
  the only delete path and stale settings keys are silently ignored
- Remove the 1500ms delete-button arm delay (armDeleteButton) from all
  delete modals; misclicks are recoverable via the undo toast
- Delete modal always shows the recoverable warning
- Log the first staged file path in staging log lines for easier support

static/js/managers/BulkManager.js

@@ -1,7 +1,6 @@
 import { state, getCurrentPageState } from '../state/index.js';
 import { showToast, showActionToast, copyToClipboard, sendLoraToWorkflow, sendEmbeddingToWorkflow, buildLoraSyntax, getNSFWLevelName } from '../utils/uiHelpers.js';
 import { handleUndoDelete } from '../utils/undoHelpers.js';
-import { armDeleteButton } from '../utils/modalUtils.js';
 import { updateCardsForBulkMode } from '../components/shared/ModelCard.js';
 import { modalManager } from './ModalManager.js';
 import { getModelApiClient, resetAndReload } from '../api/modelApiFactory.js';
@@ -630,7 +629,6 @@ export class BulkManager {
         }
 
         modalManager.showModal('bulkDeleteModal');
-        armDeleteButton(document.getElementById('bulkDeleteModal'));
     }
 
     async confirmBulkDelete() {