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>

docker-compose.yml

@@ -0,0 +1,39 @@
+version: '3.8'
+
+services:
+  nextsnap:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    container_name: nextsnap
+    ports:
+      - "${PORT:-8000}:8000"
+    environment:
+      - FLASK_ENV=production
+      - SECRET_KEY=${SECRET_KEY:?SECRET_KEY must be set}
+      - NEXTCLOUD_URL=${NEXTCLOUD_URL:?NEXTCLOUD_URL must be set}
+      - TZ=${TZ:-UTC}
+    volumes:
+      - flask_sessions:/tmp/flask_session
+    restart: unless-stopped
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:8000/api/health"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 10s
+    networks:
+      - nextsnap-network
+    logging:
+      driver: "json-file"
+      options:
+        max-size: "10m"
+        max-file: "3"
+
+volumes:
+  flask_sessions:
+    driver: local
+
+networks:
+  nextsnap-network:
+    driver: bridge