fix(pdf-controls): add focus-visible ring to all PdfControls buttons (WCAG 2.1 §2.4.7)

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

frontend/src/lib/document/viewer/PdfControls.svelte

@@ -35,7 +35,7 @@ let {
 			onclick={onPrev}
 			disabled={currentPage <= 1}
 			aria-label="Zurück"
-			class="min-h-[44px] min-w-[44px] rounded p-2 text-ink-3 transition hover:bg-surface/10 disabled:opacity-40"
+			class="min-h-[44px] min-w-[44px] rounded p-2 text-ink-3 transition hover:bg-surface/10 focus-visible:ring-2 focus-visible:ring-brand-navy focus-visible:ring-offset-1 disabled:opacity-40"
 		>
 			<svg class="h-4 w-4" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
 				<path stroke-linecap="round" stroke-linejoin="round" d="M15 19l-7-7 7-7" />
@@ -52,7 +52,7 @@ let {
 			onclick={onNext}
 			disabled={!isLoaded || currentPage >= totalPages}
 			aria-label="Weiter"
-			class="min-h-[44px] min-w-[44px] rounded p-2 text-ink-3 transition hover:bg-surface/10 disabled:opacity-40"
+			class="min-h-[44px] min-w-[44px] rounded p-2 text-ink-3 transition hover:bg-surface/10 focus-visible:ring-2 focus-visible:ring-brand-navy focus-visible:ring-offset-1 disabled:opacity-40"
 		>
 			<svg class="h-4 w-4" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
 				<path stroke-linecap="round" stroke-linejoin="round" d="M9 5l7 7-7 7" />
@@ -65,7 +65,7 @@ let {
 		<button
 			onclick={onZoomOut}
 			aria-label="Verkleinern"
-			class="min-h-[44px] min-w-[44px] rounded p-2 text-ink-3 transition hover:bg-surface/10"
+			class="min-h-[44px] min-w-[44px] rounded p-2 text-ink-3 transition hover:bg-surface/10 focus-visible:ring-2 focus-visible:ring-brand-navy focus-visible:ring-offset-1"
 		>
 			<svg class="h-4 w-4" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
 				<circle cx="11" cy="11" r="8" />
@@ -75,7 +75,7 @@ let {
 		<button
 			onclick={onZoomIn}
 			aria-label="Vergrößern"
-			class="min-h-[44px] min-w-[44px] rounded p-2 text-ink-3 transition hover:bg-surface/10"
+			class="min-h-[44px] min-w-[44px] rounded p-2 text-ink-3 transition hover:bg-surface/10 focus-visible:ring-2 focus-visible:ring-brand-navy focus-visible:ring-offset-1"
 		>
 			<svg class="h-4 w-4" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
 				<circle cx="11" cy="11" r="8" />
@@ -90,7 +90,7 @@ let {
 			onclick={onToggleAnnotations}
 			aria-label={showAnnotations ? m.pdf_annotations_hide() : m.pdf_annotations_show()}
 			aria-pressed={showAnnotations}
-			class="flex min-h-[44px] min-w-[44px] items-center gap-1.5 rounded px-3 py-2 font-sans text-xs transition {showAnnotations
+			class="flex min-h-[44px] min-w-[44px] items-center gap-1.5 rounded px-3 py-2 font-sans text-xs transition focus-visible:ring-2 focus-visible:ring-brand-navy focus-visible:ring-offset-1 {showAnnotations
 				? 'text-ink-2 hover:bg-surface/10'
 				: 'bg-surface/10 text-primary'}"
 		>

frontend/src/lib/document/viewer/PdfControls.svelte.spec.ts

@@ -66,6 +66,35 @@ describe('PdfControls — annotation toggle contrast (WCAG 2.1 AA)', () => {
 	});
 });
 
+describe('PdfControls — focus rings (WCAG 2.1 §2.4.7)', () => {
+	it('annotation toggle button has focus-visible:ring-2 focus ring', async () => {
+		const { container } = render(PdfControls, {
+			...defaultProps,
+			annotationCount: 2,
+			showAnnotations: false
+		});
+		const allButtons = container.querySelectorAll('button');
+		const annotationBtn = Array.from(allButtons).find((b) =>
+			b.getAttribute('aria-label')?.toLowerCase().includes('annotierungen')
+		);
+		expect(annotationBtn).not.toBeNull();
+		expect(annotationBtn!.className).toContain('focus-visible:ring-2');
+	});
+
+	it('icon-only nav/zoom buttons each have focus-visible:ring-2 focus ring', async () => {
+		const { container } = render(PdfControls, { ...defaultProps });
+		const allButtons = container.querySelectorAll('button');
+		const iconOnlyButtons = Array.from(allButtons).filter((b) => {
+			const label = b.getAttribute('aria-label') ?? '';
+			return ['zurück', 'weiter', 'verkleinern', 'vergrößern'].includes(label.toLowerCase());
+		});
+		expect(iconOnlyButtons).toHaveLength(4);
+		for (const btn of iconOnlyButtons) {
+			expect(btn.className).toContain('focus-visible:ring-2');
+		}
+	});
+});
+
 describe('PdfControls — touch targets (WCAG 2.2 §2.5.8)', () => {
 	it('annotation toggle button has min-h-[44px] touch target', async () => {
 		const { container } = render(PdfControls, {