feat(pwa): Admin-Tab "App" mit Install + Sync + Cache-Reset

Neuer vierter Admin-Tab (Smartphone-Icon) mit drei Karten:
1. Installieren — fängt beforeinstallprompt (Android), zeigt
   iOS-Teilen-Hinweis, sonst Info "nicht verfügbar".
2. Offline-Synchronisation — Status + "Jetzt synchronisieren"-
   Button, disabled wenn offline.
3. Cache — "Offline-Cache leeren" löscht alle kochwas-*-Caches
   via caches.keys() + delete.

install-prompt.svelte.ts hält das deferred-Event und die Plattform
(android/ios/other) per UA-Detection.

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

src/lib/client/install-prompt.svelte.ts

@@ -0,0 +1,44 @@
+// Captures the beforeinstallprompt event (Android Chrome) and holds it for
+// manual triggering by the user. On iOS Safari this event does not exist —
+// we detect the browser via UserAgent and show an info hint instead.
+class InstallPromptStore {
+  available = $state(false);
+  platform = $state<'android' | 'ios' | 'other'>('other');
+  private deferred: BeforeInstallPromptEvent | null = null;
+
+  init(): void {
+    if (typeof window === 'undefined') return;
+    this.platform = detectPlatform();
+    window.addEventListener('beforeinstallprompt', (e) => {
+      e.preventDefault();
+      this.deferred = e as BeforeInstallPromptEvent;
+      this.available = true;
+    });
+    window.addEventListener('appinstalled', () => {
+      this.deferred = null;
+      this.available = false;
+    });
+  }
+
+  async prompt(): Promise<void> {
+    if (!this.deferred) return;
+    await this.deferred.prompt();
+    this.deferred = null;
+    this.available = false;
+  }
+}
+
+function detectPlatform(): 'android' | 'ios' | 'other' {
+  const ua = navigator.userAgent;
+  if (/iPhone|iPad|iPod/i.test(ua)) return 'ios';
+  if (/Android/i.test(ua)) return 'android';
+  return 'other';
+}
+
+// Minimal type for the Chrome-specific event
+type BeforeInstallPromptEvent = Event & {
+  prompt: () => Promise<void>;
+  userChoice: Promise<{ outcome: 'accepted' | 'dismissed' }>;
+};
+
+export const installPrompt = new InstallPromptStore();

src/routes/+layout.svelte

@@ -15,6 +15,7 @@
   import Toast from '$lib/components/Toast.svelte';
   import SyncIndicator from '$lib/components/SyncIndicator.svelte';
   import { network } from '$lib/client/network.svelte';
+  import { installPrompt } from '$lib/client/install-prompt.svelte';
   import { registerServiceWorker } from '$lib/client/sw-register';
   import type { SearchHit } from '$lib/server/recipes/search-local';
   import type { WebHit } from '$lib/server/search/searxng';
@@ -207,6 +208,7 @@
     void searchFilterStore.load();
     void pwaStore.init();
     network.init();
+    installPrompt.init();
     void registerServiceWorker();
     document.addEventListener('click', handleClickOutside);
     document.addEventListener('keydown', handleKey);

src/routes/admin/+layout.svelte

@@ -1,13 +1,14 @@
 <script lang="ts">
   import { page } from '$app/stores';
-  import { Globe, Users, DatabaseBackup, type Icon } from 'lucide-svelte';
+  import { Globe, Users, DatabaseBackup, Smartphone, type Icon } from 'lucide-svelte';
 
   let { children } = $props();
 
   const items: { href: string; label: string; icon: typeof Icon }[] = [
     { href: '/admin/domains', label: 'Domains', icon: Globe },
     { href: '/admin/profiles', label: 'Profile', icon: Users },
-    { href: '/admin/backup', label: 'Backup', icon: DatabaseBackup }
+    { href: '/admin/backup', label: 'Backup', icon: DatabaseBackup },
+    { href: '/admin/app', label: 'App', icon: Smartphone }
   ];
 </script>
 

src/routes/admin/app/+page.svelte

@@ -0,0 +1,142 @@
+<script lang="ts">
+  import { Download, RefreshCw, Trash2 } from 'lucide-svelte';
+  import { installPrompt } from '$lib/client/install-prompt.svelte';
+  import { syncStatus } from '$lib/client/sync-status.svelte';
+  import { network } from '$lib/client/network.svelte';
+  import { confirmAction } from '$lib/client/confirm.svelte';
+  import { toastStore } from '$lib/client/toast.svelte';
+  import { requireOnline } from '$lib/client/require-online';
+
+  function triggerInstall() {
+    void installPrompt.prompt();
+  }
+
+  function triggerSync() {
+    if (!requireOnline('Das Synchronisieren')) return;
+    navigator.serviceWorker?.controller?.postMessage({ type: 'sync-check' });
+  }
+
+  async function clearCache() {
+    const ok = await confirmAction({
+      title: 'Offline-Cache leeren?',
+      message:
+        'Alle lokal gespeicherten Rezepte und Bilder werden entfernt. Beim nächsten Online-Start werden sie neu geladen.',
+      confirmLabel: 'Leeren',
+      destructive: true
+    });
+    if (!ok) return;
+    const keys = await caches.keys();
+    await Promise.all(keys.filter((k) => k.startsWith('kochwas-')).map((k) => caches.delete(k)));
+    toastStore.success('Cache geleert. Lade jetzt neu.');
+  }
+
+  function formatTime(ts: number | null): string {
+    if (ts === null) return 'noch nicht';
+    return new Date(ts).toLocaleString('de-DE');
+  }
+</script>
+
+<h1>App</h1>
+<p class="intro">Einstellungen für die Installation und den Offline-Cache.</p>
+
+<section class="card">
+  <h2>Installieren</h2>
+  {#if installPrompt.platform === 'ios'}
+    <p>
+      Öffne das Teilen-Menü in Safari und wähle <strong
+        >„Zum Home-Bildschirm hinzufügen"</strong
+      >.
+    </p>
+  {:else if installPrompt.available}
+    <button type="button" class="btn primary" onclick={triggerInstall}>
+      <Download size={16} strokeWidth={2} /> Als App installieren
+    </button>
+  {:else}
+    <p class="muted">
+      Installation aktuell nicht möglich (entweder schon installiert oder Browser unterstützt es
+      nicht).
+    </p>
+  {/if}
+</section>
+
+<section class="card">
+  <h2>Offline-Synchronisation</h2>
+  {#if syncStatus.state.kind === 'syncing'}
+    <p>Lädt gerade: {syncStatus.state.current}/{syncStatus.state.total} Rezepte.</p>
+  {:else if syncStatus.state.kind === 'error'}
+    <p class="error">Fehler: {syncStatus.state.message}</p>
+  {:else}
+    <p>Zuletzt synchronisiert: {formatTime(syncStatus.lastSynced)}</p>
+  {/if}
+  <button type="button" class="btn" onclick={triggerSync} disabled={!network.online}>
+    <RefreshCw size={16} strokeWidth={2} /> Jetzt synchronisieren
+  </button>
+</section>
+
+<section class="card">
+  <h2>Cache</h2>
+  <p class="muted">Nur bei Problemen: entfernt alle Offline-Daten.</p>
+  <button type="button" class="btn danger" onclick={clearCache}>
+    <Trash2 size={16} strokeWidth={2} /> Offline-Cache leeren
+  </button>
+</section>
+
+<style>
+  h1 {
+    font-size: 1.3rem;
+    margin: 0 0 0.5rem;
+  }
+  .intro {
+    color: #666;
+    margin: 0 0 1rem;
+    font-size: 0.95rem;
+  }
+  .card {
+    background: white;
+    border: 1px solid #e4eae7;
+    border-radius: 12px;
+    padding: 1rem;
+    margin-bottom: 0.75rem;
+  }
+  .card h2 {
+    margin: 0 0 0.5rem;
+    font-size: 1rem;
+    color: #2b6a3d;
+  }
+  .card p {
+    margin: 0 0 0.6rem;
+    font-size: 0.93rem;
+  }
+  .muted {
+    color: #888;
+  }
+  .error {
+    color: #c53030;
+  }
+  .btn {
+    display: inline-flex;
+    align-items: center;
+    gap: 0.4rem;
+    padding: 0.55rem 0.9rem;
+    border: 1px solid #cfd9d1;
+    background: white;
+    border-radius: 10px;
+    cursor: pointer;
+    font-size: 0.92rem;
+    min-height: 40px;
+    font-family: inherit;
+  }
+  .btn.primary {
+    background: #2b6a3d;
+    color: white;
+    border: 0;
+  }
+  .btn.danger {
+    color: #c53030;
+    border-color: #f1b4b4;
+  }
+  .btn:disabled {
+    opacity: 0.55;
+    cursor: not-allowed;
+  }
+</style>