feat: Add Digital Signature and Validate Signature tools

New Features:
- Digital Signature tool: Sign PDFs with X.509 certificates (PFX/PEM)
  - Visible and invisible signatures
  - All pages, first page, last page, or custom page selection
  - Dynamic signature height based on text content
  - Custom signature text, image, and styling options

- Validate Signature tool: Verify digital signatures in PDFs
  - Extract and parse PKCS#7 signatures
  - View signer and issuer certificate details
  - Check certificate validity and expiry
  - Optional custom X.509 certificate for trust verification
  - Full/partial coverage detection

Infrastructure:
- Added Cloudflare Worker CORS proxy for certificate chain fetching
- Updated README with new tools and proxy deployment instructions

Documentation:
- Added Digital Signature and Validate Signature to README tools table
- Added CORS proxy deployment guide for self-hosters

src/js/utils/libreoffice-loader.ts

@@ -6,7 +6,8 @@
  */
 
 import { WorkerBrowserConverter } from '@matbee/libreoffice-converter/browser';
-import { getWasmBaseUrl, getWasmFallbackUrl, isCdnEnabled } from '../config/wasm-cdn-config.js';
+
+const LIBREOFFICE_LOCAL_PATH = import.meta.env.BASE_URL + 'libreoffice-wasm/';
 
 export interface LoadProgress {
     phase: 'loading' | 'initializing' | 'converting' | 'complete' | 'ready';
@@ -24,12 +25,9 @@ export class LibreOfficeConverter {
     private initialized = false;
     private initializing = false;
     private basePath: string;
-    private localPath: string;
 
     constructor(basePath?: string) {
-        // Use CDN if available, otherwise use provided basePath or default local path
-        this.basePath = basePath || getWasmBaseUrl('libreoffice');
-        this.localPath = getWasmFallbackUrl('libreoffice');
+        this.basePath = basePath || LIBREOFFICE_LOCAL_PATH;
     }
 
     async initialize(onProgress?: ProgressCallback): Promise<void> {
@@ -49,14 +47,12 @@ export class LibreOfficeConverter {
         try {
             progressCallback?.({ phase: 'loading', percent: 0, message: 'Loading conversion engine...' });
 
-            const workerPath = isCdnEnabled() ? this.localPath : this.basePath;
-
             this.converter = new WorkerBrowserConverter({
                 sofficeJs: `${this.basePath}soffice.js`,
                 sofficeWasm: `${this.basePath}soffice.wasm.gz`,
                 sofficeData: `${this.basePath}soffice.data.gz`,
-                sofficeWorkerJs: `${workerPath}soffice.worker.js`,
-                browserWorkerJs: `${workerPath}browser.worker.global.js`,
+                sofficeWorkerJs: `${this.basePath}soffice.worker.js`,
+                browserWorkerJs: `${this.basePath}browser.worker.global.js`,
                 verbose: false,
                 onProgress: (info: { phase: string; percent: number; message: string }) => {
                     if (progressCallback && !this.initialized) {