fix(bulk-edit): a11y + i18n hardening (Leonie blockers 1–4 + quick concerns)

B1 — i18n the archive-box / archive-folder labels and add helper text.
Karton/Mappe were hardcoded German and broke EN/ES locales (WCAG 3.1.2).

B2 — drop the hardcoded German aria-label on the onboarding callout.
role="note" + the visible localised text is self-describing; the redundant
label was overriding the translated content for AT users on EN/ES.

B3 — Escape clears the bulk selection while the bar is visible. Adds an
"Esc: Auswahl aufheben" hint visible at ≥ sm (WCAG 2.1.1).

B4 — /documents and /enrich reserve pb-32 when the bulk-selection bar is
visible so it doesn't occlude the last row or pagination (WCAG 1.4.10).

Folded in three Leonie quick-concerns:
 - C5: badge text-[10px] → text-[11px], raw text-gray-600 →
        design-token text-ink-2 (dark-mode safe)
 - C7: aria-live="polite" on bulk-selection-count
 - C11: "Alles aufheben" → "Auswahl aufheben" (DE/EN/ES) — disambiguates
        from "discard the operation entirely"

Refs #225, PR #331

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

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

@@ -379,10 +379,12 @@ async function retrySave() {
 			>
 				{#if mode === 'edit'}
 					<!-- Onboarding callout: tells the user that empty fields are skipped
-						 and that tags/receivers are added rather than replaced. -->
+						 and that tags/receivers are added rather than replaced.
+						 No aria-label — role=note + the visible text content is
+						 self-describing; an aria-label would override that text for
+						 AT users on non-DE locales. -->
 					<div
 						role="note"
-						aria-label="Hinweis zur Massenbearbeitung"
 						data-testid="bulk-edit-callout"
 						class="rounded-sm border border-accent/40 bg-accent/15 px-4 py-3 text-sm text-ink-2"
 					>