Implement modular monolith architecture for better code organization and maintainability

[Copilot]

This PR transforms the backend from a traditional layered architecture to a modular monolith architecture, organizing code by business domains rather than technical layers.

Architecture Transformation

Before (Layered Architecture):

src/
├── controllers/    # All controllers mixed together
├── services/       # All services mixed together  
├── routes/         # All routes mixed together
├── validators/     # All validators mixed together
└── middlewares/    # All middlewares mixed together

After (Domain-based Modules):

src/
└── modules/
    ├── user/           # Complete user domain
    ├── category/       # Complete category domain
    ├── provider/       # Complete provider domain
    ├── company/        # Complete company domain
    ├── service/        # Complete service domain
    └── shared/         # Reusable cross-cutting components

Key Changes

1. Domain-based Organization

Each business domain now has its own module containing all related functionality:

• User Module: Authentication, profiles, user management
• Category Module: Hierarchical category management
• Provider Module: Service provider profiles and management
• Company Module: Company/organization management
• Service Module: Service listings and management
• Shared Module: Common utilities, middlewares, types, and error handling

2. Enhanced Type Safety

• Added comprehensive TypeScript interfaces for each domain
• Created shared common types and domain-specific types
• Implemented proper type exports through module index files

3. Centralized Error Handling

• Created domain-specific error classes extending a base DomainError
• Implemented centralized error handling middleware
• Added proper HTTP status code mapping for different error types

4. Repository Pattern Foundation

• Added repository interfaces for future data access abstraction
• Prepared foundation for dependency injection and better testability

5. Clean Module Boundaries

Each module follows a consistent structure:

• index.ts - Clean module exports
• types.ts - Domain-specific TypeScript interfaces
• *.controller.ts - HTTP request handling
• *.service.ts - Business logic
• *.route.ts - Route definitions
• *.validator.ts - Input validation schemas

Benefits Achieved

• Better Separation of Concerns: Code organized by business domain rather than technical function
• Improved Maintainability: Changes are localized to specific domains
• Enhanced Testability: Modules can be tested in isolation
• Scalability Foundation: Individual modules can be extracted into microservices when needed
• Developer Experience: Better code discoverability and organization
• Type Safety: Comprehensive TypeScript coverage across all domains

Migration Safety

• ✅ All existing functionality preserved
• ✅ Build process working correctly
• ✅ Import paths updated throughout codebase
• ✅ No breaking changes to API endpoints
• ✅ Removed duplicate/typo files (catagory → category)

The modular monolith architecture provides a solid foundation for scaling the application while maintaining clean separation of concerns and clear domain boundaries.

Fixes #11.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• binaries.prisma.sh
  • Triggering command: node scripts/postinstall.js (dns block)
  • Triggering command: node /home/REDACTED/work/backend/backend/node_modules/.bin/prisma -v (dns block)
  • Triggering command: node /home/REDACTED/work/backend/backend/node_modules/.bin/prisma generate (dns block)
• checkpoint.prisma.io

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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