feat(security,build): add COOP/COEP headers and improve PDF viewer initialization

- Add Cross-Origin-Opener-Policy and Cross-Origin-Embedder-Policy headers to nginx.conf for enhanced security
- Create serve.json configuration file with security headers for local development
- Update npm scripts to use vite preview instead of serve package for consistency
- Fix PDF viewer file parameter handling to prevent fallback to default URL
- Enable annotation editor mode by default in PDF viewers (annotationEditorMode: 1)
- Improve PDF preference management by clearing conflicting annotation editor settings before loading
- Update iframe URL construction to use URL API for proper origin handling
- Refactor annotation viewer setup to use eventBus for stamp button activation instead of direct DOM manipulation
- Add localStorage preference configuration for signature editor and permissions in sign tool
- Enhance security posture by implementing COOP/COEP headers required for SharedArrayBuffer and cross-origin isolation

scripts/update-version.js

@@ -0,0 +1,64 @@
+#!/usr/bin/env node
+
+/**
+ * Script to update version numbers in HTML files from package.json
+ * Run this script whenever you need to sync HTML versions with package.json
+ */
+
+import fs from 'fs';
+import path from 'path';
+import { fileURLToPath } from 'url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+
+// Read version from package.json
+const packageJson = JSON.parse(
+  fs.readFileSync(path.join(__dirname, '..', 'package.json'), 'utf8')
+);
+const version = packageJson.version;
+
+// HTML files to update
+const htmlFiles = [
+  'index.html',
+  'about.html',
+  'contact.html',
+  'faq.html',
+  'privacy.html',
+  'terms.html',
+  'src/pages/add-stamps.html',
+  'src/pages/bookmark.html',
+  'src/pages/json-to-pdf.html',
+  'src/pages/pdf-multi-tool.html',
+  'src/pages/pdf-to-json.html',
+  'src/pages/table-of-contents.html',
+];
+
+console.log(`Updating version to ${version} in HTML files...`);
+
+let updatedCount = 0;
+
+htmlFiles.forEach((file) => {
+  const filePath = path.join(__dirname, '..', file);
+  
+  if (!fs.existsSync(filePath)) {
+    console.log(`⚠️  Skipping ${file} (not found)`);
+    return;
+  }
+
+  let content = fs.readFileSync(filePath, 'utf8');
+  
+  // Replace version in <span id="app-version">X.X.X</span>
+  const regex = /(<span id="app-version">)[^<]+(<\/span>)/g;
+  const newContent = content.replace(regex, `$1${version}$2`);
+  
+  if (content !== newContent) {
+    fs.writeFileSync(filePath, newContent, 'utf8');
+    console.log(`✓ Updated ${file}`);
+    updatedCount++;
+  } else {
+    console.log(`- ${file} (already up to date)`);
+  }
+});
+
+console.log(`\nDone! Updated ${updatedCount} file(s) to version ${version}`);