refactor(Architecture): Refactor application to DDD and Onion Architecture

[azjezz]

This commit restructures the entire application to follow the principles of Domain-Driven Design (DDD) and Onion Architecture. The goal is to isolate the core domain, make the application more testable, and decouple it from framework-specific details.

The src directory is now organized into four distinct layers, with dependencies flowing only inwards:

• Domain Layer (src/Domain):

  • Contains the core business logic, including rich entities, repository interfaces, and domain events.
  • This layer is now completely independent of any framework or external library. Doctrine and validation attributes have been removed from entities and moved to external XML mapping files in src/Resource.

• Application Layer (src/Application):

  • Orchestrates the domain logic by implementing the application's use cases.
  • Contains the Commands, Queries, and their respective Handlers.

• Infrastructure Layer (src/Infrastructure):

  • Provides the concrete implementations for interfaces defined in the inner layers (e.g., Doctrine repositories, Messenger buses).
  • The Symfony Kernel (Kernel.php) now resides here, clearly marking it as an infrastructure detail.

• Representation Layer (src/Representation):

  • Contains all user-facing components, such as controllers, forms, and voters.

Additionally, all framework-specific configuration (bundles, packages, routes), templates, and assets have been moved from the project root into a dedicated src/Resource directory. This makes a clean separation between the application's code and the framework's configuration.