Doc endpoints

[LauraLangdon]

Done so far

• Added static OpenAPI 3.1.0 spec at schemas/aggregated-public-information.json
• Integrated starlight-openapi plugin into docs site — generates API reference pages at /api-reference/

Still to do

• Review and consider styling — the default starlight-openapi rendering is functional but plain. Example of a more polished Starlight API docs site for reference: https://docs.cookie-api.com/en/docs/roblox-group-manager/endpoints/user/user-management/. As is there are also a11y contrast issues, etc.
• Revisit whether to add internal API docs (website, needs-assessment)