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/temp-dir/index.js

@@ -0,0 +1,13 @@
+'use strict';
+const fs = require('fs');
+const os = require('os');
+
+const tempDirectorySymbol = Symbol.for('__RESOLVED_TEMP_DIRECTORY__');
+
+if (!global[tempDirectorySymbol]) {
+	Object.defineProperty(global, tempDirectorySymbol, {
+		value: fs.realpathSync(os.tmpdir())
+	});
+}
+
+module.exports = global[tempDirectorySymbol];