feat: add genealogy showcase scaffold

[gcomneno]

Summary

• add a selectable genealogy-oriented client scaffold
• model people through generic catalog items and free-form relationships
• add a visitor relationship overview using the shared RelationshipGraph
• provide localized navigation, sitemap integration, tests, and operational documentation

Architecture

• keeps genealogy vocabulary and conventions inside scaffold content
• introduces no genealogy-specific core validation, database, loader, enum, or runtime service
• imports RelationshipGraph through giadaware-ui-components/visitor
• preserves canonical /items/{id} links and non-tree relationships

Verification

• node --test test/genealogy-scaffold.test.js
• affected integration tests: 32/32 passed
• npm test: 326/326 passed
• npm run content:validate
• npm run check: 0 errors and 0 warnings
• npm run build
• git diff --check

Closes #210