Implement template system and PWA enhancements

Phase 6 - Template System:
- Add TemplateLayer component for background/overlay rendering
- Add SlotPlaceholder component with visual indicators for empty slots
- Add useTemplate hook with auto-crop and drag constraint functions
- Update templates.js with slot definitions for team-sport template
- Integrate template system into DesignCanvas and App
- Add slot upload UI in TemplatesTab sidebar

Phase 9 - PWA Improvements:
- Add Workbox caching rules for HuggingFace LFS, templates, and API
- Change registerType to 'prompt' for update notifications
- Add service worker update handler in main.jsx
- Add refresh prompt UI in PWAInstall component

Phase 10 - Responsive and Accessibility:
- Add responsive CSS media queries for tablet/mobile layouts
- Add OfflineIndicator component with online/offline detection
- Add focus trap and keyboard navigation to PhotoPreEditor
- Add aria labels and screen reader support to modal

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

client/vite.config.js

@@ -6,7 +6,7 @@ export default defineConfig({
   plugins: [
     react(),
     VitePWA({
-      registerType: 'autoUpdate',
+      registerType: 'prompt',
       includeAssets: ['favicon.ico', 'pwa-192x192.svg', 'pwa-512x512.svg'],
       manifest: {
         name: 'Apparel Designer',
@@ -54,6 +54,21 @@ export default defineConfig({
               },
             },
           },
+          // HuggingFace LFS (Large File Storage) for model weights
+          {
+            urlPattern: /^https:\/\/cdn-lfs\.huggingface\.co\/.*/i,
+            handler: 'CacheFirst',
+            options: {
+              cacheName: 'transformers-lfs',
+              expiration: {
+                maxEntries: 10,
+                maxAgeSeconds: 60 * 60 * 24 * 30,
+              },
+              cacheableResponse: {
+                statuses: [0, 200],
+              },
+            },
+          },
           {
             urlPattern: /^\/api\/uploads\/.*/i,
             handler: 'CacheFirst',
@@ -65,6 +80,37 @@ export default defineConfig({
               },
             },
           },
+          // Template data caching
+          {
+            urlPattern: /^\/api\/templates\/.*/i,
+            handler: 'StaleWhileRevalidate',
+            options: {
+              cacheName: 'template-data',
+              expiration: {
+                maxEntries: 20,
+                maxAgeSeconds: 60 * 60 * 24 * 7,
+              },
+              cacheableResponse: {
+                statuses: [0, 200],
+              },
+            },
+          },
+          // API responses caching
+          {
+            urlPattern: /^\/api\/.*/i,
+            handler: 'NetworkFirst',
+            options: {
+              cacheName: 'api-responses',
+              expiration: {
+                maxEntries: 50,
+                maxAgeSeconds: 300,
+              },
+              cacheableResponse: {
+                statuses: [0, 200],
+              },
+              networkTimeoutSeconds: 3,
+            },
+          },
           {
             urlPattern: /^https:\/\/fonts\.googleapis\.com\/.*/i,
             handler: 'StaleWhileRevalidate',