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/app.js

@@ -0,0 +1,111 @@
+// NextSnap - Main application logic
+'use strict';
+
+const NextSnap = {
+    version: '1.0.0',
+    isOnline: navigator.onLine,
+
+    init() {
+        console.log(`NextSnap v${this.version} initializing...`);
+        this.setupConnectivityMonitoring();
+        this.setupServiceWorkerMessaging();
+        this.checkHealth();
+    },
+
+    setupConnectivityMonitoring() {
+        // Update online status on events
+        window.addEventListener('online', () => {
+            console.log('Network: Online');
+            this.isOnline = true;
+            this.updateConnectivityIndicator();
+            // Sync is handled by SyncEngine's own online listener in sync.js
+        });
+
+        window.addEventListener('offline', () => {
+            console.log('Network: Offline');
+            this.isOnline = false;
+            this.updateConnectivityIndicator();
+        });
+
+        // Initial status
+        this.updateConnectivityIndicator();
+    },
+
+    updateConnectivityIndicator() {
+        const indicator = document.querySelector('.connectivity-indicator');
+        if (!indicator) return;
+
+        indicator.classList.remove('online', 'offline', 'syncing');
+
+        if (this.isOnline) {
+            indicator.classList.add('online');
+            indicator.title = 'Online';
+        } else {
+            indicator.classList.add('offline');
+            indicator.title = 'Offline';
+        }
+    },
+
+    setSyncingStatus(isSyncing) {
+        const indicator = document.querySelector('.connectivity-indicator');
+        if (!indicator) return;
+
+        if (isSyncing) {
+            indicator.classList.add('syncing');
+            indicator.title = 'Syncing...';
+        } else {
+            indicator.classList.remove('syncing');
+            indicator.title = this.isOnline ? 'Online' : 'Offline';
+        }
+    },
+
+    setupServiceWorkerMessaging() {
+        if ('serviceWorker' in navigator && navigator.serviceWorker.controller) {
+            // Listen for messages from service worker
+            navigator.serviceWorker.addEventListener('message', (event) => {
+                console.log('Message from SW:', event.data);
+            });
+        }
+    },
+
+    // Force service worker update
+    async updateServiceWorker() {
+        if ('serviceWorker' in navigator) {
+            const registration = await navigator.serviceWorker.getRegistration();
+            if (registration) {
+                await registration.update();
+                console.log('Service worker update check triggered');
+            }
+        }
+    },
+
+    // Clear all caches (for debugging)
+    async clearCache() {
+        if ('serviceWorker' in navigator && navigator.serviceWorker.controller) {
+            navigator.serviceWorker.controller.postMessage({
+                type: 'CLEAR_CACHE'
+            });
+            console.log('Cache clear requested');
+        }
+    },
+
+    async checkHealth() {
+        try {
+            const response = await fetch('/api/health');
+            const data = await response.json();
+            console.log('Health check:', data);
+        } catch (error) {
+            console.error('Health check failed:', error);
+        }
+    }
+};
+
+// Initialize when DOM is ready
+if (document.readyState === 'loading') {
+    document.addEventListener('DOMContentLoaded', () => NextSnap.init());
+} else {
+    NextSnap.init();
+}
+
+// Make NextSnap globally available
+window.NextSnap = NextSnap;