feat(pwa): manifest.webmanifest + icons + theme-color + Workbox SW

Phase 10: adds PWA manifest, placeholder icons (192/512), manifest/theme-color meta tags to both app layout files, and VitePWA plugin with manifest:false + Workbox runtimeCaching (CacheFirst assets, NetworkOnly HTML).

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

public/manifest.webmanifest

@@ -0,0 +1,22 @@
+{
+    "name": "Lernschiff",
+    "short_name": "Lernschiff",
+    "description": "Kinderlernplattform für 3–14 Jahre",
+    "start_url": "/",
+    "display": "standalone",
+    "background_color": "#f0eee9",
+    "theme_color": "#f0eee9",
+    "lang": "de",
+    "icons": [
+        {
+            "src": "/icons/icon-192.png",
+            "sizes": "192x192",
+            "type": "image/png"
+        },
+        {
+            "src": "/icons/icon-512.png",
+            "sizes": "512x512",
+            "type": "image/png"
+        }
+    ]
+}

vite.config.js

@@ -1,6 +1,7 @@
 import { defineConfig } from 'vite';
 import laravel from 'laravel-vite-plugin';
 import tailwindcss from '@tailwindcss/vite';
+import { VitePWA } from 'vite-plugin-pwa';
 
 export default defineConfig({
     plugins: [
@@ -9,5 +10,28 @@ export default defineConfig({
             input: ['resources/css/app.css', 'resources/js/app.js', 'resources/js/auth.js'],
             refresh: true,
         }),
+        VitePWA({
+            registerType: 'autoUpdate',
+            manifest: false,
+            workbox: {
+                runtimeCaching: [
+                    {
+                        urlPattern: /\.(?:js|css|woff2?|png|svg|ico)$/i,
+                        handler: 'CacheFirst',
+                        options: {
+                            cacheName: 'assets-cache',
+                            expiration: {
+                                maxEntries: 100,
+                                maxAgeSeconds: 60 * 60 * 24 * 30,
+                            },
+                        },
+                    },
+                    {
+                        urlPattern: /^https?:\/\/.+\/(?!api)/,
+                        handler: 'NetworkOnly',
+                    },
+                ],
+            },
+        }),
     ],
 });