refactor(sql): reduce connection pool size and remove PostgreSQL optimizations

perf(sales): implement aggressive database performance optimizations for sale creation

perf(sales): implement bulk insert optimization and add performance monitoring

feat(schema): Enforce TRANS schema compliance across all POS tables

feat(database): Add comprehensive PostgreSQL connection management and configuration

feat: Add staff_code field to staff schemas and services

feat(staff): Implement PostgreSQL integration for staff management and add validation schemas