Demo Server Guide / Docker guide

**Summary**
During internal discussions, we agreed to keep the demo server as a lightweight and simple solution to run a DWH instance without the need for additional dependencies such as Wildfly or complex configurations.

However, the current tutorial lacks detailed guidance on efficient usage and deployment. Especially for non-technical users, it’s important to provide an easy-to-follow, step-by-step tutorial.

**What should be improved?**
A clear and beginner-friendly tutorial should be written.

**The tutorial should include:**
- 📦 How to deploy the demo server locally (e.g., via Docker)
- 🏗️ Basic setup instructions for a working DWH instance
- 📤 Instructions on how to send CDA documents to the server
- ✅ Examples and sample files where possible (e.g., minimal CDA)

**Target Audience**
- Users with limited technical background
- People who just want to quickly evaluate or test the system without learning deployment technologies

**Why is this needed?**
- Lower the barrier for newcomers and testers
- Enable stakeholders and healthcare partners to easily spin up test instances
- Improve support and reproducibility in workshops, evaluations, and project onboarding
- Lower the barrier for newcomers and testers