Add screenshots to README installation guide

[victorsoriadrp]

Context

The installation section in the README explains the commands but does not show what the user will see after running them. Screenshots dramatically improve the first-time experience.

Acceptance criteria

• Screenshot of the empty workspace landing page after first launch
• Screenshot of "Create workspace" modal
• Screenshot of an EAM view (Application Dashboard) populated with the ArchiSurance example
• Screenshots placed in website/screenshots/ and referenced from README via relative path
• Each screenshot annotated with a one-line caption

Notes for first-time contributors

You only need a working Docker Compose deploy and a screen capture tool. Use the included example model (examples/archisurance-extended.xml) to populate the views.