feat: Implement Trade Relationships Module with CRUD operations and supplier discovery

refactor(database): enforce TRANS schema compliance and simplify table initialization

refactor(database): migrate tables to trans schema and consolidate initialization

chore(stock_take): complete legacy cleanup and finalize master-detail migration

refactor(database): consolidate shared database base and fix foreign key schema references

refactor: reorganize constants and clean up legacy code structure

merchant issue

feat: Enhance PostgreSQL connection configuration with support for alternative environment variables, robust URI assembly, detailed logging, and new documentation.

feat: Add PostgreSQL diagnostic script and comprehensive PO creation tests with supporting documentation.

feat: Migrate PostgreSQL interactions to SQLAlchemy's async engine, improving connection management, query parameterization, and URI configuration.

feat(postgres): add ssl support and connection retry logic

feat(scm): Implement PostgreSQL PO/GRN module with consolidated schema