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/js/logic/digital-sign-pdf-page.ts

@@ -400,7 +400,7 @@ async function handleCertFile(file: File): Promise<void> {
           certStatus.className = 'text-xs text-green-400';
         }
       }
-    } catch (error) {
+    } catch {
       const certStatus = getElement<HTMLDivElement>('cert-status');
       if (certStatus) {
         certStatus.textContent = 'Failed to parse PEM file';