fix(a11y): fix ProgressRing text label contrast and add no-restricted-syntax lint rule for text-accent

ProgressRing used text-accent (#a1dcd8) on a percentage text label —
same WCAG 2.1 AA failure as #341. Switched to text-primary.

Also adds ESLint no-restricted-syntax rule (scoped to *.svelte files) that
blocks future text-accent usage in JavaScript string literals inside Svelte
class expressions. The rule caught both violations at once; both are now fixed.
The rule is scoped to .svelte files so test assertions against 'text-accent'
strings in .spec.ts files are unaffected.

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

frontend/eslint.config.js

@@ -40,6 +40,26 @@ export default defineConfig(
 				parser: ts.parser,
 				svelteConfig
 			}
+		},
+		rules: {
+			// text-accent resolves to #a1dcd8 in light mode (1.52:1 on white — WCAG fail).
+			// layout.css documents it as decorative-only (borders, icon tints, bg fills).
+			// For any text label use text-primary or text-ink instead. This rule catches
+			// the pattern where text-accent appears inside a JavaScript string literal
+			// (e.g. conditional ternary class expressions in Svelte templates).
+			'no-restricted-syntax': [
+				'error',
+				{
+					selector: 'Literal[value=/\\btext-accent\\b/]',
+					message:
+						'text-accent is decorative-only (#a1dcd8 in light mode = 1.52:1 contrast — WCAG fail). Use text-primary or text-ink-2 for text labels.'
+				},
+				{
+					selector: 'TemplateLiteral > TemplateElement[value.raw=/\\btext-accent\\b/]',
+					message:
+						'text-accent is decorative-only (#a1dcd8 in light mode = 1.52:1 contrast — WCAG fail). Use text-primary or text-ink-2 for text labels.'
+				}
+			]
 		}
 	}
 );

frontend/src/lib/components/PdfControls.svelte

@@ -91,7 +91,7 @@ let {
 			aria-label={showAnnotations ? m.pdf_annotations_hide() : m.pdf_annotations_show()}
 			class="flex items-center gap-1.5 rounded px-2 py-1 font-sans text-xs transition {showAnnotations
 				? 'text-ink-2 hover:bg-surface/10'
-				: 'bg-surface/10 text-accent'}"
+				: 'bg-surface/10 text-primary'}"
 		>
 			<svg
 				class="h-3.5 w-3.5 shrink-0"

frontend/src/lib/components/PdfControls.svelte.spec.ts

@@ -0,0 +1,67 @@
+import { vi, describe, it, expect, afterEach } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import { page } from 'vitest/browser';
+
+import PdfControls from './PdfControls.svelte';
+
+afterEach(cleanup);
+
+const defaultProps = {
+	currentPage: 1,
+	totalPages: 3,
+	isLoaded: true,
+	showAnnotations: false,
+	annotationCount: 0,
+	onPrev: vi.fn(),
+	onNext: vi.fn(),
+	onZoomIn: vi.fn(),
+	onZoomOut: vi.fn(),
+	onToggleAnnotations: vi.fn()
+};
+
+describe('PdfControls — annotation toggle visibility', () => {
+	it('renders annotation toggle when annotationCount is greater than zero', async () => {
+		render(PdfControls, { ...defaultProps, annotationCount: 3 });
+		await expect
+			.element(page.getByRole('button', { name: /annotierungen anzeigen/i }))
+			.toBeInTheDocument();
+	});
+
+	it('does not render annotation toggle when annotationCount is zero', async () => {
+		render(PdfControls, { ...defaultProps, annotationCount: 0 });
+		await expect
+			.element(page.getByRole('button', { name: /annotierungen/i }))
+			.not.toBeInTheDocument();
+	});
+});
+
+describe('PdfControls — annotation toggle label', () => {
+	it('shows "Annotierungen anzeigen" label when annotations are hidden', async () => {
+		render(PdfControls, { ...defaultProps, annotationCount: 2, showAnnotations: false });
+		const btn = page.getByRole('button', { name: /annotierungen anzeigen/i });
+		await expect.element(btn).toBeInTheDocument();
+	});
+
+	it('shows "Annotierungen verbergen" label when annotations are visible', async () => {
+		render(PdfControls, { ...defaultProps, annotationCount: 2, showAnnotations: true });
+		const btn = page.getByRole('button', { name: /annotierungen verbergen/i });
+		await expect.element(btn).toBeInTheDocument();
+	});
+});
+
+describe('PdfControls — annotation toggle contrast (WCAG 2.1 AA)', () => {
+	it('uses text-primary class on annotation toggle button when annotations are hidden', 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('text-primary');
+		expect(annotationBtn!.className).not.toContain('text-accent');
+	});
+});

frontend/src/lib/components/ProgressRing.svelte

@@ -19,7 +19,7 @@ let { percentage }: { percentage: number } = $props();
 		/>
 	</svg>
 	<span
-		class="block text-center font-sans text-xs font-bold {percentage > 0 ? 'text-accent' : 'text-gray-400'}"
+		class="block text-center font-sans text-xs font-bold {percentage > 0 ? 'text-primary' : 'text-gray-400'}"
 	>
 		{percentage}%
 	</span>

frontend/src/lib/components/ProgressRing.svelte.spec.ts

@@ -25,12 +25,12 @@ describe('ProgressRing', () => {
 		expect(el.className).toContain('text-gray-400');
 	});
 
-	it('renders a mint-colored label when percentage is > 0', async () => {
+	it('renders a primary-colored label when percentage is > 0', async () => {
 		render(ProgressRing, { percentage: 75 });
 		const label = page.getByText('75%');
 		await expect.element(label).toBeInTheDocument();
 		const el = (await label.element()) as HTMLElement;
-		expect(el.className).toContain('text-accent');
+		expect(el.className).toContain('text-primary');
 	});
 
 	it('renders a fully filled arc for 100%', async () => {