Refactor database access into DAO/Repository layer

[kmuwanga83]

📌 Problem

Database operations are tightly coupled with business logic or controllers, making the code hard to maintain and scale.

🎯 Objective

Implement a DAO/Repository layer to improve separation of concerns.

✅ Tasks

• Create repository classes for:
  • Patient
  • Appointment
  • Medical records
• Move SQL/database logic from controllers/services into repositories
• Use interfaces where applicable

🧪 Acceptance Criteria

• Controllers do not directly access the database
• Repository layer handles all persistence logic
• Codebase becomes modular and maintainable