Refactor to unify scripts/categories as Executable

This commit consolidates scripts and categories under a unified
'Executable' concept. This simplifies the architecture and improves code
readability.

- Introduce subfolders within `src/domain` to segregate domain elements.
- Update class and interface names by removing the 'I' prefix in
  alignment with new coding standards.
- Replace 'Node' with 'Executable' to clarify usage; reserve 'Node'
  exclusively for the UI's tree component.

tests/unit/shared/Stubs/FunctionCodeStub.ts

@@ -1,4 +1,4 @@
-import type { IFunctionCode } from '@/application/Parser/Script/Compiler/Function/ISharedFunction';
+import type { IFunctionCode } from '@/application/Parser/Executable/Script/Compiler/Function/ISharedFunction';
 
 export class FunctionCodeStub implements IFunctionCode {
   public execute = 'execute code (function-code-stub)';