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>

Makefile

@@ -0,0 +1,69 @@
+.PHONY: help build up down restart logs shell test clean dev prod
+
+help:
+	@echo "NextSnap - Available Commands:"
+	@echo "  make build     - Build Docker image"
+	@echo "  make up        - Start containers (production)"
+	@echo "  make down      - Stop containers"
+	@echo "  make restart   - Restart containers"
+	@echo "  make logs      - View container logs"
+	@echo "  make shell     - Open shell in container"
+	@echo "  make test      - Run tests"
+	@echo "  make clean     - Remove containers and volumes"
+	@echo "  make dev       - Start development environment"
+	@echo "  make prod      - Start production environment"
+
+build:
+	docker-compose build
+
+up:
+	docker-compose up -d
+
+down:
+	docker-compose down
+
+restart:
+	docker-compose restart
+
+logs:
+	docker-compose logs -f --tail=100
+
+shell:
+	docker-compose exec nextsnap /bin/bash
+
+test:
+	docker-compose exec nextsnap pytest tests/
+
+clean:
+	docker-compose down -v
+	docker system prune -f
+
+dev:
+	docker-compose -f docker-compose.dev.yml up
+
+dev-build:
+	docker-compose -f docker-compose.dev.yml build
+
+dev-down:
+	docker-compose -f docker-compose.dev.yml down
+
+prod:
+	docker-compose up -d
+
+status:
+	docker-compose ps
+
+health:
+	@curl -f http://localhost:8000/api/health || echo "Health check failed"
+
+backup-sessions:
+	docker run --rm -v nextsnap_flask_sessions:/data -v $(PWD):/backup \
+		alpine tar czf /backup/sessions_backup_$(shell date +%Y%m%d_%H%M%S).tar.gz -C /data .
+
+restore-sessions:
+	@read -p "Enter backup file name: " file; \
+	docker run --rm -v nextsnap_flask_sessions:/data -v $(PWD):/backup \
+		alpine tar xzf /backup/$$file -C /data
+
+generate-secret:
+	@python -c "import secrets; print(secrets.token_hex(32))"