Add people and museum entity documentation

[karilint]

Summary

• Add an entity documentation index for the current entity docs folder
• Add People documentation covering com_people, com_users, person routes, and permission behavior
• Add Museums documentation covering com_mlist, now_mus, routes, and locality links
• Link the new entity docs from the main documentation index

Closes #723

Validation

• git diff --check
• npm run lint (via commit hook)
• npm run tsc (via commit hook)