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/address/lib/address.d.ts

@@ -0,0 +1,28 @@
+export = address;
+
+declare interface Address {
+  ip: string;
+  ipv6: string;
+  mac: string;
+}
+
+declare type AddressCallback = (err: Error, addr: Address) => void;
+declare type MacCallback = (err: Error, addr: string) => void;
+declare type DnsCallback = (err: Error, servers: string[]) => void;
+
+declare function address(interfaceName: string, callback: AddressCallback): void;
+declare function address(callback: AddressCallback): void;
+
+declare namespace address {
+  const MAC_IP_RE: RegExp;
+  const MAC_RE: RegExp;
+
+  function dns(filepath: string, callback: DnsCallback): void;
+  function dns(callback: DnsCallback): void;
+
+  function ip(interfaceName?: string): any;
+  function ipv6(interfaceName?: string): any;
+
+  function mac(interfaceName: string, callback: MacCallback): void;
+  function mac(callback: MacCallback): void;
+}