feat(schema): add an address record and map it to other formats

[Adeniyikayodee]

A small JSON object for passing a whole Nigerian address between systems, built around the postcode reference this repository already defines.

• Schema: docs/schemas/address.schema.json requires only postcode (a postcode reference) and country. It adds optional names (state, lga, locality), street_address, description, and location. The MCP suite validates its examples, rejects malformed records, and resolves the nested reference from the file beside it.
• Page: docs/address-record.md says where each field comes from and maps the record onto ISO 20022, FHIR, schema.org, and vCard. Names come from NIPOST's lookup at level 2, since the libraries hold no name tables.
• Rule worth noting: only a building-level code goes into another format's postcode field. A coarser code is a prefix and stays in the record.

The payments note gives field lengths from the Federal Reserve's ISO 20022 sheet (16 characters for the postcode, so the hyphenated code fits). It states no date for Swift retiring unstructured addresses, because Swift's pages and bank guidance disagreed when I checked.