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/uri-js/dist/esnext/schemes/urn.d.ts

@@ -0,0 +1,10 @@
+import { URISchemeHandler, URIComponents, URIOptions } from "../uri";
+export interface URNComponents extends URIComponents {
+    nid?: string;
+    nss?: string;
+}
+export interface URNOptions extends URIOptions {
+    nid?: string;
+}
+declare const handler: URISchemeHandler<URNComponents, URNOptions>;
+export default handler;