Refactor services and repositories to remove stored procedures in favor of direct ORM queries

feat(customers): add endpoint to retrieve projects associated with a specific customer with pagination

feat(projects): add endpoints to retrieve project customers and customer details with pagination

Implement employee management features; add employee model, repository, service, and controller with CRUD operations, and include unit tests for validation

Implement project listing with pagination and sorting; add repository and service methods, update models and schemas, and include unit tests for functionality

Implement customer listing with pagination and ordering via stored procedure; update models, services, and tests