feat(frontend): add relativeTimeDe helper for dashboard meta lines

Pure function with injectable now — lets the dashboard enrichment block
render "vor 2 Min." / "vor 3 Std." / "vor 2 Tagen" without clock-based
test flakiness. Reuses the existing comment_time_minutes / _hours /
_days Paraglide keys, no new translations needed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/lib/relativeTime.spec.ts

@@ -0,0 +1,34 @@
+import { describe, it, expect } from 'vitest';
+import { relativeTimeDe } from './relativeTime';
+
+const NOW = new Date('2026-04-20T12:00:00Z');
+
+describe('relativeTimeDe', () => {
+	it('returns minutes for a gap under one hour', () => {
+		const from = new Date('2026-04-20T11:58:00Z');
+		expect(relativeTimeDe(from, NOW)).toContain('2');
+		expect(relativeTimeDe(from, NOW)).toMatch(/Minute/i);
+	});
+
+	it('returns hours for a gap between 1 and 24 hours', () => {
+		const from = new Date('2026-04-20T09:00:00Z');
+		expect(relativeTimeDe(from, NOW)).toContain('3');
+		expect(relativeTimeDe(from, NOW)).toMatch(/Stunde/i);
+	});
+
+	it('returns days for a gap of 24 hours or more', () => {
+		const from = new Date('2026-04-18T12:00:00Z');
+		expect(relativeTimeDe(from, NOW)).toContain('2');
+		expect(relativeTimeDe(from, NOW)).toMatch(/Tag/i);
+	});
+
+	it('rounds minutes to the nearest whole number', () => {
+		const from = new Date('2026-04-20T11:58:20Z');
+		expect(relativeTimeDe(from, NOW)).toContain('2');
+	});
+
+	it('handles zero gap as 0 minutes', () => {
+		expect(relativeTimeDe(NOW, NOW)).toMatch(/0/);
+		expect(relativeTimeDe(NOW, NOW)).toMatch(/Minute/i);
+	});
+});

frontend/src/lib/relativeTime.ts

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+import * as m from '$lib/paraglide/messages.js';
+
+export function relativeTimeDe(from: Date, now: Date = new Date()): string {
+	const minutes = Math.round((now.getTime() - from.getTime()) / 60_000);
+	if (minutes < 60) return m.comment_time_minutes({ count: minutes });
+	if (minutes < 1440) return m.comment_time_hours({ count: Math.round(minutes / 60) });
+	return m.comment_time_days({ count: Math.round(minutes / 1440) });
+}