lib/
  app/                       → app-wide modules (theme, router, DI, env)
    router.dart              → global routing (go_router)
    theme.dart               → app theme and styling
    di.dart                  → dependency injection (providers, locator)

  core/                      → shared, generic & stable components
    network/                 → Dio client, interceptors
    storage/                 → secure/local storage abstractions
    error/                   → Failure, AppException, guards
    utils/                   → formatters, validators, helpers
    result.dart              → Either/Result type

  modules/
    inventory/
      data/
        models/              → DTOs (Json)
        sources/             → remote/local data sources
        repositories/        → implementations (InventoryRepositoryImpl)
      domain/
        entities/            → pure Dart objects (business entities)
        repositories/        → abstract definitions (InventoryRepository)
        usecases/            → business logic (AddItem, ScanBarcode, …)
      presentation/
        pages/
          inventory_page.dart
          add_item_page.dart
        controllers/         → state management (Riverpod/BLoC) & presenters
        widgets/             → feature-specific UI components
      inventory_routes.dart  → go_router routes for this feature

    budget/                  → same structure as inventory
    expenses/                → same structure as inventory
    auth/                    → same structure as inventory

  main.dart                  → application entry point

Layered Flow

Data Source → Repository Impl → Repository Abstraction → UseCase → Controller → UI (Pages/Widgets)