Fix func-style lint warning in formatRelativeDate test

Convert the cfg helper from an arrow expression to a function declaration
to match the project's ESLint config.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: myieye

frontend/viewer/src/lib/components/ui/format/format-relative-date.test.ts

@@ -1,11 +1,9 @@
 import {describe, expect, it} from 'vitest';
 import {formatRelativeDate} from './format-relative-date-fn.svelte';
 
-const cfg = (now: Date, smallestUnit: 'milliseconds' | 'seconds' | 'minutes' | 'hours' = 'seconds') => ({
-  defaultValue: 'NEVER',
-  now,
-  smallestUnit,
-});
+function cfg(now: Date, smallestUnit: 'milliseconds' | 'seconds' | 'minutes' | 'hours' = 'seconds') {
+  return {defaultValue: 'NEVER', now, smallestUnit};
+}
 
 describe('formatRelativeDate', () => {
   it('returns defaultValue for nullish input', () => {