feat(projects): add playground architecture diagram and notes

Update the Playground entry on the projects page: diagram,
prerender, privacy and operations bullets, one challenge,
one learning, and the Traefik, nginx and Tailscale technologies.

src/app/constants/AssetsConstants.ts

@@ -42,6 +42,7 @@ export class AssetsConstants {
   ];
 
   static readonly CLAUDE_BOX_DIAGRAM = '/assets/projects/claude-in-a-box/1.svg';
+  static readonly PLAYGROUND_DIAGRAM = '/assets/projects/playground/architecture.svg';
   static readonly TBP_DIAGRAM = '/assets/projects/to-be-played/architecture.svg';
   static readonly TRIBBLE_DIAGRAM = '/assets/projects/tribble-the-homeserver/architecture.svg';