feat: mirror-all-to-NAS, content reset (danger zone), in-app changelog + CHANGELOG.md, How-To refresh

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNQ8ghPfzAfsyVYd6HgFb6

src/pages/api/admin/storage.ts

@@ -1,5 +1,5 @@
 import type { APIRoute } from 'astro';
-import { storageStats, runRetention, purgeSources } from '../../../lib/maintenance';
+import { storageStats, runRetention, purgeSources, mirrorAllToNas } from '../../../lib/maintenance';
 import { one } from '../../../lib/db';
 
 export const prerender = false;
@@ -12,6 +12,7 @@ export const GET: APIRoute = async () => json({ stats: await storageStats() });
 export const POST: APIRoute = async ({ request }) => {
   const b = await request.json().catch(() => ({}));
   if (b.action === 'purge_sources') return json(await purgeSources());
+  if (b.action === 'mirror_all') return json(await mirrorAllToNas());
   if (b.action === 'retention') {
     const s = await one<{ retention_days: number | null }>('SELECT retention_days FROM settings WHERE id=1');
     if (!s?.retention_days) return json({ error: 'Keine Aufbewahrungsfrist gesetzt.' }, 400);