docs(context7): add rules for prefixes, SQL, and the address record

[Adeniyikayodee]

Context7's listing for this repository serves four rules and has not indexed the prefix type, the SQL files, or the address record. This updates context7.json so the next index carries them.

• Description: now names SQL, the prefix type, and the address record.
• Rules: nine, up from four. The new ones tell an agent which package name to install on each registry, which form to store and which to write, to cut a code to a prefix with truncate instead of slicing the string, to use the PostgreSQL domain and the correct DuckDB constraint, and how to pass an address between systems.

Every rule is under the schema's 255-character limit, and no key is outside the schema.