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/memfs/lib/internal/buffer.d.ts

@@ -0,0 +1,15 @@
+/// <reference types="node" />
+import { Buffer } from 'buffer';
+declare const bufferAllocUnsafe: (size: number) => Buffer;
+declare const bufferFrom: {
+    (arrayBuffer: ArrayBuffer | SharedArrayBuffer, byteOffset?: number | undefined, length?: number | undefined): Buffer;
+    (data: readonly any[]): Buffer;
+    (data: Uint8Array): Buffer;
+    (obj: {
+        valueOf(): string | object;
+    } | {
+        [Symbol.toPrimitive](hint: "string"): string;
+    }, byteOffset?: number | undefined, length?: number | undefined): Buffer;
+    (str: string, encoding?: string | undefined): Buffer;
+};
+export { Buffer, bufferAllocUnsafe, bufferFrom };