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/edit-metadata-page.ts

@@ -1,13 +1,9 @@
+import { EditMetadataState } from '@/types';
 import { showLoader, hideLoader, showAlert } from '../ui.js';
 import { downloadFile, formatBytes } from '../utils/helpers.js';
 import { createIcons, icons } from 'lucide';
 import { PDFDocument as PDFLibDocument, PDFName, PDFString } from 'pdf-lib';
 
-interface EditMetadataState {
-    file: File | null;
-    pdfDoc: PDFLibDocument | null;
-}
-
 const pageState: EditMetadataState = {
     file: null,
     pdfDoc: null,