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/jiti/dist/utils.d.ts

@@ -0,0 +1,8 @@
+import type { PackageJson } from "pkg-types";
+export declare function getCacheDir(): string;
+export declare function isDir(filename: string): boolean;
+export declare function isWritable(filename: string): boolean;
+export declare function md5(content: string, len?: number): string;
+export declare function detectLegacySyntax(code: string): RegExpMatchArray | null;
+export declare function isObject(val: any): boolean;
+export declare function readNearestPackageJSON(path: string): PackageJson | undefined;