fix(bulk-edit): pluralization, edit-mode CTA, error UI, real loading state

Elicit C1+C3 — bulk-selection count uses ICU-style plural keys
(bulk_edit_n_selected_one / _other) so n=1 reads as "1 Dokument" instead
of "1 Dokumente". Save CTA in edit mode reads "Anwenden" via the existing
bulk_edit_save_button key; UploadSaveBar grew an editMode prop. Multi-
chunk progress text is now visible (not aria-only).

Felix C2 — bulk-edit page wires the backend error code through
parseBackendError + getErrorMessage instead of falling back to a generic
internal_error.

Felix C5 — editAllMatching no longer swallows fetch failures: the button
shows an inline error with the backend-mapped message (e.g. when the
filter cap is exceeded).

Leonie C8 — replace the literal "…" loading glyph on /documents/bulk-edit
with a spinner + role=status + aria-live=polite + visible "Loading
documents…" text.

Leonie C9 — partial-failure card and bulk-edit page error card now use
the design-system `text-danger` / `bg-danger/10` / `border-danger/40`
tokens (dark-mode safe) instead of raw red palette values.

Leonie C10 + C13 — German plural fixed; EN badges retensed
("+ added" → "+ will be added", "replaced" → "will replace") to match
the future-tense intent of DE/ES.

Refs #225, PR #331

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

frontend/src/routes/documents/+page.svelte

@@ -8,6 +8,7 @@ import DocumentList from '../DocumentList.svelte';
 import Pagination from '$lib/components/Pagination.svelte';
 import BulkSelectionBar from '$lib/components/document/BulkSelectionBar.svelte';
 import { bulkSelectionStore } from '$lib/stores/bulkSelection.svelte';
+import { getErrorMessage, parseBackendError } from '$lib/errors';
 import * as m from '$lib/paraglide/messages.js';
 
 let { data } = $props();
@@ -141,16 +142,18 @@ $effect(() => {
 });
 
 let editingAll = $state(false);
+let editAllError = $state<string | null>(null);
 
 /**
  * Fast path: replace the current selection with every document matching the
  * active filter (across all pages) and jump to the bulk-edit screen. The
- * /api/documents/ids endpoint is uncapped — chunking happens at PATCH time
- * inside the bulk-edit page's save handler.
+ * /api/documents/ids endpoint is hard-capped (5000 results); on cap overflow
+ * the backend returns BULK_EDIT_TOO_MANY_IDS, which we surface inline.
  */
 async function editAllMatching() {
 	if (editingAll) return;
 	editingAll = true;
+	editAllError = null;
 	try {
 		const params = buildSearchParams({
 			q: data.q || '',
@@ -168,12 +171,15 @@ async function editAllMatching() {
 		params.delete('dir');
 		const res = await fetch(`/api/documents/ids?${params.toString()}`);
 		if (!res.ok) {
-			editingAll = false;
+			const backend = await parseBackendError(res);
+			editAllError = getErrorMessage(backend?.code);
 			return;
 		}
 		const ids: string[] = await res.json();
 		bulkSelectionStore.setAll(ids);
 		await goto('/documents/bulk-edit');
+	} catch {
+		editAllError = m.bulk_edit_all_x_failed();
 	} finally {
 		editingAll = false;
 	}
@@ -229,7 +235,7 @@ $effect(() => {
 	/>
 
 	{#if data.canWrite && data.totalElements > 0}
-		<div class="mb-2 flex justify-end">
+		<div class="mb-2 flex flex-col items-end gap-1">
 			<button
 				type="button"
 				onclick={editAllMatching}
@@ -239,6 +245,11 @@ $effect(() => {
 			>
 				{m.bulk_edit_all_x({ count: data.totalElements })}
 			</button>
+			{#if editAllError}
+				<p role="alert" class="text-xs text-danger" data-testid="bulk-edit-all-x-error">
+					{editAllError}
+				</p>
+			{/if}
 		</div>
 	{/if}