Add NextSnap PWA with photo gallery viewer and continuous capture

Offline-first photo capture app for Nextcloud with:
- Camera capture with continuous mode (auto-reopens after each photo)
- File browser with fullscreen image gallery, swipe navigation, and rename
- Upload queue with background sync engine
- Admin panel for Nextcloud user management
- Service worker for offline-first caching (v13)

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

app/static/js/sync_fix.txt

@@ -0,0 +1,6 @@
+    async updateRecentPhotos() {
+        // Delegate to Camera module if available
+        if (typeof Camera !== 'undefined' && Camera.updateRecentPhotos) {
+            await Camera.updateRecentPhotos();
+        }
+    },