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/domain/ScriptCodeFactory.spec.ts

@@ -1,4 +1,4 @@
-import { createScriptCode } from '@/domain/ScriptCodeFactory';
+import { createScriptCode } from '@/domain/Executables/Script/Code/ScriptCodeFactory';
 
 describe('ScriptCodeFactory', () => {
   describe('createScriptCode', () => {