Initial commit: Developer Tools MVP with visual editor

- Complete React app with 7 developer tools
- JSON Tool with visual structured editor
- Serialize Tool with visual structured editor
- URL, Base64, CSV/JSON, Beautifier, Diff tools
- Responsive navigation with dropdown menu
- Dark/light mode toggle
- Mobile-responsive design with sticky header
- All tools working with copy/paste functionality

src/App.js

@@ -0,0 +1,33 @@
+import React from 'react';
+import { BrowserRouter as Router, Routes, Route } from 'react-router-dom';
+import Layout from './components/Layout';
+import Home from './pages/Home';
+import JsonTool from './pages/JsonTool';
+import SerializeTool from './pages/SerializeTool';
+import UrlTool from './pages/UrlTool';
+import Base64Tool from './pages/Base64Tool';
+import CsvJsonTool from './pages/CsvJsonTool';
+import BeautifierTool from './pages/BeautifierTool';
+import DiffTool from './pages/DiffTool';
+import './index.css';
+
+function App() {
+  return (
+    <Router>
+      <Layout>
+        <Routes>
+          <Route path="/" element={<Home />} />
+          <Route path="/json" element={<JsonTool />} />
+          <Route path="/serialize" element={<SerializeTool />} />
+          <Route path="/url" element={<UrlTool />} />
+          <Route path="/base64" element={<Base64Tool />} />
+          <Route path="/csv-json" element={<CsvJsonTool />} />
+          <Route path="/beautifier" element={<BeautifierTool />} />
+          <Route path="/diff" element={<DiffTool />} />
+        </Routes>
+      </Layout>
+    </Router>
+  );
+}
+
+export default App;