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>

.env.example

@@ -0,0 +1,18 @@
+# NextSnap Environment Configuration
+# Copy this file to .env and fill in your values
+
+# Flask Secret Key - CHANGE THIS IN PRODUCTION!
+# Generate with: python -c "import secrets; print(secrets.token_hex(32))"
+SECRET_KEY=your-secret-key-here
+
+# Nextcloud Instance URL
+NEXTCLOUD_URL=https://nextcloud.example.com
+
+# Port to expose the application (default: 8000)
+PORT=8000
+
+# Timezone (default: UTC)
+TZ=UTC
+
+# Optional: Flask Environment (development or production)
+FLASK_ENV=production