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/ScriptCodeStub.ts

@@ -1,6 +1,6 @@
-import type { IScriptCode } from '@/domain/IScriptCode';
+import type { ScriptCode } from '@/domain/Executables/Script/Code/ScriptCode';
 
-export class ScriptCodeStub implements IScriptCode {
+export class ScriptCodeStub implements ScriptCode {
   public execute = `[${ScriptCodeStub.name}] default execute code`;
 
   public revert = `[${ScriptCodeStub.name}] default revert code`;