feat(bulk-edit): add BulkSelectionBar and Alle-X-editieren fast path

- BulkSelectionBar component: sticky bottom bar shown only when canWrite
  and selection is non-empty. Buttons meet WCAG 44px touch targets and
  iOS safe-area inset is honoured.
- Bar mounted on /documents and /enrich.
- Alle X editieren button on /documents replaces the selection with
  every UUID matching the active filter (via /api/documents/ids) and
  jumps to /documents/bulk-edit.

Refs #225

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

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

@@ -0,0 +1,46 @@
+<script lang="ts">
+import { goto } from '$app/navigation';
+import { m } from '$lib/paraglide/messages.js';
+import { bulkSelectionStore } from '$lib/stores/bulkSelection.svelte';
+
+let { canWrite }: { canWrite: boolean } = $props();
+
+const count = $derived(bulkSelectionStore.size);
+
+function openBulkEdit() {
+	goto('/documents/bulk-edit');
+}
+
+function clearAll() {
+	bulkSelectionStore.clear();
+}
+</script>
+
+{#if canWrite && count > 0}
+	<div
+		data-testid="bulk-selection-bar"
+		class="fixed right-0 bottom-0 left-0 z-30 flex items-center justify-between border-t border-line bg-surface px-4 py-3 pb-[max(0.75rem,env(safe-area-inset-bottom))] shadow-[0_-2px_8px_rgba(0,0,0,0.06)] sm:px-6"
+	>
+		<span class="font-sans text-sm font-medium text-ink" data-testid="bulk-selection-count">
+			{m.bulk_edit_n_selected({ count })}
+		</span>
+		<div class="flex items-center gap-2">
+			<button
+				type="button"
+				onclick={clearAll}
+				class="inline-flex min-h-[44px] items-center px-4 py-2 font-sans text-sm font-medium text-ink-2 transition-colors hover:text-ink"
+				data-testid="bulk-clear-all"
+			>
+				{m.bulk_edit_clear_all()}
+			</button>
+			<button
+				type="button"
+				onclick={openBulkEdit}
+				class="inline-flex min-h-[44px] items-center bg-primary px-5 py-2 font-sans text-xs font-bold tracking-widest text-primary-fg uppercase transition-colors hover:bg-primary/90"
+				data-testid="bulk-edit-open"
+			>
+				{m.bulk_edit_button()}
+			</button>
+		</div>
+	</div>
+{/if}