[Feature] Add Docker Compose development environment

[Rexus]

What

Set up a Docker Compose-based development environment for Archflow.

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Why

Archflow should be easy to start locally and should establish a consistent development setup early. This will later also be the base for adding NetBox to the stack.

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Done when

• A docker-compose setup exists
• The main Archflow services can start locally
• The structure is ready for later NetBox inclusion