feat(staff): implement staff list endpoint with projection support

docs: Update merchant type terminology from uppercase to lowercase

docs: Update terminology from "salon" to "retail" for consistency

docs: Update terminology from "National cnf" to "NCNF" for consistency

docs: Update documentation and examples to use consistent terminology

feat: Add staff_code field to staff schemas and services

refactor(auth): Migrate from employees to staff module and consolidate constants

feat: Add database management script and requirements