Fix/es6 migrations models

[agaesh]

🧱 Pull Request: Refactor Models to ES Module Syntax

Overview

This pull request migrates all Sequelize model files from CommonJS (require, module.exports) to ES Module (ESM) syntax (import, export default).
The refactor ensures consistency across the project and improves compatibility with modern Node.js tooling, especially when working with ES-based controllers and services.

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Changes Included

• ✅ Migrated Department model to ES module syntax
• ✅ Migrated Instructor model to ES module syntax
• ✅ Migrated ProgramCourse model to ES module syntax
• ✅ Migrated Student model to ES module syntax
• ✅ Migrated User model to ES module syntax
• ✅ Refactored index.js for dynamic model loading using import syntax

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Benefits

• Modernized codebase for future maintainability
• Eliminates mixed module syntax issues
• Improves readability and consistency across all models
• Supports smooth integration with refactored ES-based controllers and services

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Reviewer Note:
All the models have been refactored in es style code. this will be merged with es6-migration branch without testing.

[agaesh]

This pull request have been merged into fix/es6-migration