feat(06-01): add Docker configuration for production deployment

- Create Dockerfile with multi-stage build using node:22-alpine
- Run as non-root 'nodejs' user for security
- Add HEALTHCHECK for container orchestration
- Create docker-compose.yml with taskplaner_data named volume
- Add .dockerignore to optimize build context

docker-compose.yml

@@ -0,0 +1,15 @@
+services:
+  taskplaner:
+    build: .
+    container_name: taskplaner
+    ports:
+      - "3000:3000"
+    volumes:
+      - taskplaner_data:/app/data
+    environment:
+      - NODE_ENV=production
+      - TASKPLANER_DATA_DIR=/app/data
+    restart: unless-stopped
+
+volumes:
+  taskplaner_data: