Refactor and enhance type safety across various modules

- Updated function parameters and return types in `page-preview.ts`, `pdf-decrypt.ts`, and `pymupdf-loader.ts` for improved type safety.
- Introduced type definitions for `CpdfInstance`, `PyMuPDFInstance`, and other related types to ensure better type checking.
- Enhanced error handling in `sanitize.ts` by creating a utility function for error messages.
- Removed unnecessary type assertions and improved type inference in `editor.ts`, `serialization.ts`, and `tools.test.ts`.
- Added type definitions for markdown-it plugins to improve compatibility and type safety.
- Enforced stricter TypeScript settings by enabling `noImplicitAny` in `tsconfig.json`.
- Cleaned up test files by refining type assertions and ensuring consistency in type usage.

src/tests/state.test.ts

@@ -21,7 +21,9 @@ describe('State Management', () => {
       // 1. Modify the state properties to non-default values
       state.activeTool = 'merge';
       state.files = [{ name: 'dummy.pdf', size: 1234 } as File];
-      state.pdfDoc = { numPages: 5 }; // Mock PDF document object
+      state.pdfDoc = {
+        numPages: 5,
+      } as unknown as import('pdf-lib').PDFDocument;
       state.pdfPages = [{}, {}]; // Mock page objects
       state.currentPdfUrl = 'blob:http://localhost/some-uuid';