fix(admin/system): address second-round review concerns

- Extract ImportStatus type to types.ts — removes duplication across
  +page.svelte, ImportStatusCard.svelte, and test file (Felix blocker)
- Fix H2 to match CLAUDE.md card pattern: text-xs uppercase tracking-widest
  text-ink-3 mb-5 (Leonie blocker 1)
- Add font-sans to RUNNING and DONE status labels (Leonie blocker 2)
- Add data-testid="processed-count" to count elements in both states
- Replace document.querySelector with locator API in spinner tests
- Tighten getByText('7') to getByTestId('processed-count') (Felix/Sara)

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

frontend/src/routes/admin/system/+page.svelte

@@ -2,19 +2,13 @@
 import { onDestroy } from 'svelte';
 import { m } from '$lib/paraglide/messages.js';
 import ImportStatusCard from './ImportStatusCard.svelte';
+import type { ImportStatus } from './types.js';
 
 let backfillResult: number | null = $state(null);
 let backfillLoading = $state(false);
 let backfillHashesResult: number | null = $state(null);
 let backfillHashesLoading = $state(false);
 
-type ImportStatus = {
-	state: 'IDLE' | 'RUNNING' | 'DONE' | 'FAILED';
-	statusCode: string;
-	processed: number;
-	startedAt: string | null;
-};
-
 type ThumbnailStatus = {
 	state: 'IDLE' | 'RUNNING' | 'DONE' | 'FAILED';
 	message: string;