Fix HTML Preview Tool critical bugs: PreviewFrame ref and click handler

- Fixed missing ref={previewFrameRef} on first PreviewFrame component (line 336)
  * This was causing 'PreviewFrame API not available' errors during save operations
  * Both fullscreen and normal mode PreviewFrame instances now have proper ref connection

- Fixed click handler attachment bug in setupInspectModeStyles function
  * Click handler was being skipped when styles were already injected
  * Now always attaches click handler when inspect mode is activated
  * Added proper cleanup to prevent duplicate event listeners

- Fixed variable scope issues in PreviewFrame.fresh.js
  * styleElement and cursorStyleElement now properly scoped for cleanup function
  * Added references to existing elements when styles already present

- Removed unused variables and fixed eslint warnings
  * Removed unused indentSize variable in BeautifierTool.js
  * Removed unused onSave and onDomUpdate props in PreviewFrame.fresh.js
  * Fixed unnecessary escape character in script tag

These fixes restore the Enhanced Option A DOM manipulation architecture:
- Inspector sidebar should now appear when clicking elements in inspect mode
- Save functionality should work without 'PreviewFrame ref not available' errors
- Live editing of element properties should work through PreviewFrame API
- Iframe refresh prevention during inspector operations maintained

src/components/Layout.js

@@ -1,6 +1,6 @@
 import React, { useState, useEffect, useRef } from 'react';
 import { Link, useLocation } from 'react-router-dom';
-import { Code2, Home, ChevronDown, Menu, X, Database, FileText, Link as LinkIcon, Hash, FileSpreadsheet, Wand2, GitCompare } from 'lucide-react';
+import { Code2, Home, ChevronDown, Menu, X, Database, FileText, Link as LinkIcon, Hash, FileSpreadsheet, Wand2, GitCompare, Code } from 'lucide-react';
 import ThemeToggle from './ThemeToggle';
 
 const Layout = ({ children }) => {
@@ -40,7 +40,8 @@ const Layout = ({ children }) => {
     { path: '/base64', name: 'Base64 Tool', icon: Hash, description: 'Base64 encode/decode' },
     { path: '/csv-json', name: 'CSV/JSON Tool', icon: FileSpreadsheet, description: 'Convert CSV ↔ JSON' },
     { path: '/beautifier', name: 'Beautifier Tool', icon: Wand2, description: 'Beautify/minify code' },
-    { path: '/diff', name: 'Diff Tool', icon: GitCompare, description: 'Compare text differences' }
+    { path: '/diff', name: 'Diff Tool', icon: GitCompare, description: 'Compare text differences' },
+    { path: '/html-preview', name: 'HTML Preview', icon: Code, description: 'Render HTML, CSS, JS' }
   ];
 
   return (