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/@babel/runtime/helpers/esm/tsRewriteRelativeImportExtensions.js

@@ -0,0 +1,6 @@
+function tsRewriteRelativeImportExtensions(t, e) {
+  return "string" == typeof t && /^\.\.?\//.test(t) ? t.replace(/\.(tsx)$|((?:\.d)?)((?:\.[^./]+)?)\.([cm]?)ts$/i, function (t, s, r, n, o) {
+    return s ? e ? ".jsx" : ".js" : !r || n && o ? r + n + "." + o.toLowerCase() + "js" : t;
+  }) : t;
+}
+export { tsRewriteRelativeImportExtensions as default };