feat(admin/system): add system maintenance page under /admin/system

Moves the system maintenance panel out of the old tab-based admin page
and into a dedicated route. Renders maintenance cards with spinner state
and success message on completion.

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

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

@@ -0,0 +1,78 @@
+<script lang="ts">
+import { m } from '$lib/paraglide/messages.js';
+
+let backfillResult: number | null = $state(null);
+let backfillLoading = $state(false);
+let backfillHashesResult: number | null = $state(null);
+let backfillHashesLoading = $state(false);
+
+async function backfillVersions() {
+	backfillLoading = true;
+	backfillResult = null;
+	try {
+		const res = await fetch('/api/admin/backfill-versions', { method: 'POST' });
+		if (res.ok) {
+			const data = await res.json();
+			backfillResult = data.count;
+		}
+	} finally {
+		backfillLoading = false;
+	}
+}
+
+async function backfillFileHashes() {
+	backfillHashesLoading = true;
+	backfillHashesResult = null;
+	try {
+		const res = await fetch('/api/admin/backfill-file-hashes', { method: 'POST' });
+		if (res.ok) {
+			const data = await res.json();
+			backfillHashesResult = data.count;
+		}
+	} finally {
+		backfillHashesLoading = false;
+	}
+}
+</script>
+
+<div class="flex-1 overflow-y-auto p-6">
+	<div class="mx-auto max-w-2xl space-y-5">
+		<!-- Backfill versions -->
+		<div class="rounded-sm border border-line bg-surface p-6 shadow-sm">
+			<h2 class="mb-1 font-sans text-sm font-bold text-ink">{m.admin_system_backfill_heading()}</h2>
+			<p class="mb-4 text-sm text-ink-2">{m.admin_system_backfill_description()}</p>
+			<button
+				onclick={backfillVersions}
+				disabled={backfillLoading}
+				class="rounded-sm bg-primary px-5 py-2 font-sans text-xs font-bold tracking-widest text-primary-fg uppercase transition-opacity hover:opacity-80 disabled:cursor-not-allowed disabled:opacity-50"
+			>
+				{backfillLoading ? '…' : m.admin_system_backfill_btn()}
+			</button>
+			{#if backfillResult !== null}
+				<p class="mt-4 rounded-sm border border-green-200 bg-green-50 p-3 text-sm text-green-700">
+					{m.admin_system_backfill_success({ count: backfillResult })}
+				</p>
+			{/if}
+		</div>
+
+		<!-- Backfill file hashes -->
+		<div class="rounded-sm border border-line bg-surface p-6 shadow-sm">
+			<h2 class="mb-1 font-sans text-sm font-bold text-ink">
+				{m.admin_system_backfill_hashes_heading()}
+			</h2>
+			<p class="mb-4 text-sm text-ink-2">{m.admin_system_backfill_hashes_description()}</p>
+			<button
+				onclick={backfillFileHashes}
+				disabled={backfillHashesLoading}
+				class="rounded-sm bg-primary px-5 py-2 font-sans text-xs font-bold tracking-widest text-primary-fg uppercase transition-opacity hover:opacity-80 disabled:cursor-not-allowed disabled:opacity-50"
+			>
+				{backfillHashesLoading ? '…' : m.admin_system_backfill_hashes_btn()}
+			</button>
+			{#if backfillHashesResult !== null}
+				<p class="mt-4 rounded-sm border border-green-200 bg-green-50 p-3 text-sm text-green-700">
+					{m.admin_system_backfill_hashes_success({ count: backfillHashesResult })}
+				</p>
+			{/if}
+		</div>
+	</div>
+</div>

frontend/src/routes/admin/system/page.svelte.spec.ts

@@ -0,0 +1,34 @@
+import { afterEach, describe, expect, it } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import { page } from 'vitest/browser';
+import Page from './+page.svelte';
+
+afterEach(cleanup);
+
+describe('Admin system page', () => {
+	it('renders the backfill versions heading', async () => {
+		render(Page, {});
+		await expect.element(page.getByText(/Verlaufsdaten auffüllen/i)).toBeInTheDocument();
+	});
+
+	it('renders the backfill versions button', async () => {
+		render(Page, {});
+		await expect
+			.element(page.getByRole('button', { name: /jetzt auffüllen/i }))
+			.toBeInTheDocument();
+	});
+
+	it('renders the backfill file hashes heading', async () => {
+		render(Page, {});
+		await expect
+			.element(page.getByRole('heading', { name: /Datei-Hashes berechnen/i }))
+			.toBeInTheDocument();
+	});
+
+	it('renders the file hashes button', async () => {
+		render(Page, {});
+		await expect
+			.element(page.getByRole('button', { name: /Datei-Hashes berechnen/i }))
+			.toBeInTheDocument();
+	});
+});