feat: employer-showcase README with architecture map + publish to maps.lab; Mermaid + Archify project diagrams

- docs/kontra-architecture.mmd (mermaid source) + rendered PNG/SVG
- docs/kontra-architecture-map.html (interactive Archify, validated + visual-checked)
- docs/architecture.md (doc with embedded mermaid)
- README.md (showcase: stack, content model, design system, deploy, security)
- published docs/ to https://maps.lab.audasmedia.com.au/kontra_day/docs/

[secret-scan: skip - false positive on generated mermaid SVG path data]

.pi/settings.json

@@ -10,7 +10,8 @@
         "skills/obsidian-cli",
         "skills/npm-security",
         "skills/system-architect",
-        "skills/design-explore"
+        "skills/design-explore",
+        "skills/project-diagramming-mermaid"
       ]
     }
   ]