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

node_modules/react-dom/server.node.js

@@ -0,0 +1,17 @@
+'use strict';
+
+var l, s;
+if (process.env.NODE_ENV === 'production') {
+  l = require('./cjs/react-dom-server-legacy.node.production.min.js');
+  s = require('./cjs/react-dom-server.node.production.min.js');
+} else {
+  l = require('./cjs/react-dom-server-legacy.node.development.js');
+  s = require('./cjs/react-dom-server.node.development.js');
+}
+
+exports.version = l.version;
+exports.renderToString = l.renderToString;
+exports.renderToStaticMarkup = l.renderToStaticMarkup;
+exports.renderToNodeStream = l.renderToNodeStream;
+exports.renderToStaticNodeStream = l.renderToStaticNodeStream;
+exports.renderToPipeableStream = s.renderToPipeableStream;