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/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 () => {