feat: PWA + mobile-friendly layout

- Add vite-plugin-pwa: generates manifest, Workbox service worker, precaches app shell
- Generate icon-192, icon-512, apple-touch-icon PNGs from existing SVG logo
- Add theme-color, apple-mobile-web-app-capable, apple-touch-icon meta tags; viewport-fit=cover for notch support
- Mobile layout (< 768px): bottom tab bar (Library, Albums, Memories, Map, More) replaces top nav; sidebar becomes slide-in filter drawer with backdrop; bulk action bar clears bottom nav; safe-area insets throughout

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

vite.config.js

@@ -1,9 +1,41 @@
 import { defineConfig } from 'vite';
 import react from '@vitejs/plugin-react';
+import { VitePWA } from 'vite-plugin-pwa';
 
 export default defineConfig({
   root: 'client',
-  plugins: [react()],
+  plugins: [
+    react(),
+    VitePWA({
+      registerType: 'autoUpdate',
+      includeAssets: ['favicon.svg', 'icons/apple-touch-icon.png'],
+      manifest: {
+        name: 'Luma',
+        short_name: 'Luma',
+        description: 'Self-hosted photo manager',
+        theme_color: '#0f0f0f',
+        background_color: '#0f0f0f',
+        display: 'standalone',
+        icons: [
+          { src: '/icons/icon-192.png', sizes: '192x192', type: 'image/png' },
+          { src: '/icons/icon-512.png', sizes: '512x512', type: 'image/png', purpose: 'any maskable' },
+        ],
+      },
+      workbox: {
+        globPatterns: ['**/*.{js,css,html,svg,png,ico,woff2}'],
+        runtimeCaching: [
+          {
+            urlPattern: /^\/api\//,
+            handler: 'NetworkFirst',
+            options: {
+              cacheName: 'api-cache',
+              networkTimeoutSeconds: 5,
+            },
+          },
+        ],
+      },
+    }),
+  ],
   server: {
     port: 5173,
     proxy: {