Refactored the application's dependency injection and server setup to improve modularity and adhere to the Dependency Inversion Principle.
- Moved the instantiation of all application services from `internal/app/app.go` to the composition root in `cmd/api/main.go`.
- The `app.NewApplication` function now accepts pre-built service interfaces, making the `app` package a simple container.
- Updated `internal/testutil/integration_test_utils.go` to reflect the new DI pattern, ensuring tests align with the refactored structure.
- Corrected build errors that arose from the refactoring, including import conflicts and incorrect function calls.
- Updated `TASKS.md` to mark the 'Refactor Dependency Injection' task as complete.
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