🚀 Refactor: Migrate Codebase from CommonJS to ES6 Module

Overview

This PR completes the migration of the backend codebase from CommonJS (require/module.exports) to ES6 module syntax (import/export). The refactor improves consistency, maintainability, and alignment with modern Node.js standards.

✨ Key Changes

🔁 ES6 Module Migration

• Migrated models, controllers, services, routes, middleware, validators, config, DB setup, tests, migrations, and seeders to ES module syntax.
• Added "type": "module" to package.json to enable native ES module support.

🧩 Models

• Migrated all Sequelize models to ES modules.
• Improved model loading structure.
• Fixed: Enabled timestamps for the Department model.

🧠 Controllers & Services

• Refactored all controllers and services to ES modules.
• Improved CRUD method structure and error handling.
• Unified export patterns for better readability and consistency.
• Streamlined authentication logic (cookie/token handling).

🌐 Routes

• Converted all route files to ES6 module syntax.
• Improved clarity and organization.

⚙️ Config & Database

• Migrated configuration and database setup to ES modules.
• Fixed case-sensitivity issues (config → Config) to prevent cross-platform bugs.
• Standardized import paths for db.js and config files.

🧪 Tests

• Updated unit and integration tests to ES module syntax.
• Improved test structure and error handling.
• Removed legacy CommonJS test files and added updated .test.js equivalents.

📦 Migrations & Seeders

• Migrated all Sequelize migration and seeder files to ES6 module syntax.
• Ensured compatibility with updated Sequelize configuration.

✅ Benefits

• Modern, standardized module system
• Improved readability and maintainability
• Reduced platform-specific issues
• Cleaner exports and architecture consistency
• Better test organization and reliability

📝 Notes

• No functional business logic changes intended beyond minor fixes and cleanups.
• This PR lays the groundwork for easier future upgrades and tooling support.