build(docker): add integration tests, Dockerfile, and docker-compose for packaging

docker-compose.yml

@@ -0,0 +1,20 @@
+version: '3.8'
+
+services:
+  zugferd-service:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    ports:
+      - "5000:5000"
+    volumes:
+      - ./src:/app/src:ro
+    environment:
+      - LOG_LEVEL=INFO
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:5000/health"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 10s
+    restart: unless-stopped