feat(frontend-dapp): wagmi transport + env types for Chain 2138

- Optional http() transport for 2138 when VITE_ENABLE_CHAIN2138 set
- Document VITE_* 2138 vars in .env.example; augment vite-env.d.ts

Made-with: Cursor

frontend-dapp/src/vite-env.d.ts

@@ -1,15 +1,21 @@
 /// <reference types="vite/client" />
 
-import { EventEmitter } from 'events';
+interface ImportMetaEnv {
+  readonly VITE_ENABLE_CHAIN2138?: string
+  readonly VITE_RPC_URL_2138?: string
+  readonly VITE_EXPLORER_URL_2138?: string
+}
+
+import { EventEmitter } from 'events'
 
 interface Window {
-  Buffer: typeof Buffer;
-  EventEmitter: typeof EventEmitter;
+  Buffer: typeof Buffer
+  EventEmitter: typeof EventEmitter
 }
 
 declare global {
-  var Buffer: typeof import('buffer').Buffer;
-  var EventEmitter: typeof import('events').EventEmitter;
+  var Buffer: typeof import('buffer').Buffer
+  var EventEmitter: typeof import('events').EventEmitter
 }
 
-export {};
+export {}