feat(bulk-upload): guard discard-all with confirm dialog

Uses getConfirmService() (optional — null fallback when context is absent so
unit tests that don't exercise the discard path need no CONFIRM_KEY context)
and the new bulk_discard_confirm i18n key.

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

frontend/messages/de.json

@@ -857,6 +857,7 @@
 	"bulk_save_cta_one": "Speichern →",
 	"bulk_save_cta": "{count} speichern →",
 	"bulk_discard_all": "Alle verwerfen",
+	"bulk_discard_confirm": "Alle Dateien und eingegebenen Daten verwerfen? Diese Aktion kann nicht rückgängig gemacht werden.",
 	"bulk_add_more": "Weitere hinzufügen",
 	"bulk_scope_per_file_label": "Nur diese Datei",
 	"bulk_scope_shared_label": "Gilt für alle {count}",

frontend/messages/en.json

@@ -857,6 +857,7 @@
 	"bulk_save_cta_one": "Save →",
 	"bulk_save_cta": "Save {count} →",
 	"bulk_discard_all": "Discard all",
+	"bulk_discard_confirm": "Discard all files and entered data? This action cannot be undone.",
 	"bulk_add_more": "Add more",
 	"bulk_scope_per_file_label": "This file only",
 	"bulk_scope_shared_label": "Applies to all {count}",

frontend/messages/es.json

@@ -857,6 +857,7 @@
 	"bulk_save_cta_one": "Guardar →",
 	"bulk_save_cta": "Guardar {count} →",
 	"bulk_discard_all": "Descartar todo",
+	"bulk_discard_confirm": "¿Descartar todos los archivos y datos introducidos? Esta acción no se puede deshacer.",
 	"bulk_add_more": "Añadir más",
 	"bulk_scope_per_file_label": "Solo este archivo",
 	"bulk_scope_shared_label": "Para todos los {count}",

frontend/src/lib/components/document/BulkDocumentEditLayout.svelte

@@ -3,6 +3,8 @@ import { SvelteMap } from 'svelte/reactivity';
 import { goto } from '$app/navigation';
 import { onDestroy, untrack } from 'svelte';
 import { m } from '$lib/paraglide/messages.js';
+import { getConfirmService } from '$lib/services/confirm.svelte.js';
+import type { ConfirmService } from '$lib/services/confirm.svelte.js';
 import BulkDropZone from './BulkDropZone.svelte';
 import FileSwitcherStrip from './FileSwitcherStrip.svelte';
 import type { FileEntry } from './FileSwitcherStrip.svelte';
@@ -17,6 +19,14 @@ import type { components } from '$lib/generated/api';
 
 type Person = components['schemas']['Person'];
 
+// Optional — not available in unit tests that don't provide CONFIRM_KEY context.
+let _confirmService: ConfirmService | null;
+try {
+	_confirmService = getConfirmService();
+} catch {
+	_confirmService = null;
+}
+
 let {
 	initialSenderId = '',
 	initialSenderName = '',
@@ -77,6 +87,18 @@ function discardAll() {
 	chunkProgress = undefined;
 }
 
+async function handleDiscard() {
+	if (_confirmService) {
+		const ok = await _confirmService.confirm({
+			title: m.bulk_discard_all(),
+			body: m.bulk_discard_confirm(),
+			destructive: true
+		});
+		if (!ok) return;
+	}
+	discardAll();
+}
+
 onDestroy(() => {
 	for (const entry of files.values()) {
 		if (entry.previewUrl) URL.revokeObjectURL(entry.previewUrl);
@@ -177,7 +199,7 @@ async function save() {
 				<button
 					type="button"
 					data-testid="discard-all-btn"
-					onclick={discardAll}
+					onclick={handleDiscard}
 					class="text-xs font-medium text-red-600/70 hover:text-red-700"
 				>
 					{m.bulk_discard_all()}
@@ -289,7 +311,7 @@ async function save() {
 				fileCount={files.size}
 				chunkProgress={chunkProgress}
 				onSave={save}
-				onDiscard={discardAll}
+				onDiscard={handleDiscard}
 				disabled={saving}
 			/>
 		</div>