refactor: move all TypeScript interfaces to centralized src/js/types folder

- Create type files with barrel export via @/types alias
- Update logic files to use centralized type imports

src/js/logic/add-attachments-page.ts

@@ -1,3 +1,4 @@
+import { AddAttachmentState } from '@/types';
 import { showLoader, hideLoader, showAlert } from '../ui.js';
 import { downloadFile, formatBytes } from '../utils/helpers.js';
 import { createIcons, icons } from 'lucide';
@@ -5,12 +6,6 @@ import { PDFDocument as PDFLibDocument } from 'pdf-lib';
 
 const worker = new Worker(import.meta.env.BASE_URL + 'workers/add-attachments.worker.js');
 
-interface AddAttachmentState {
-    file: File | null;
-    pdfDoc: PDFLibDocument | null;
-    attachments: File[];
-}
-
 const pageState: AddAttachmentState = {
     file: null,
     pdfDoc: null,