refactor(merchant): move address formatting logic to pipeline stage

fix(projections): ensure formatted_address has fallback value

feat(merchant): enhance merchant details with associate data

fix: correct field name from 'associate' to 'associates' in projection

refactor(models): rename staff to associate across codebase

refactor(geospatial): use $arrayElemAt for location coordinates access

feat(models): add merchant_category to recommended fields

feat(services): replace RuntimeError with HTTPException in helper functions