fix(electron): use dynamic network config for balance queries

Previously Home.tsx hardcoded testnet RPC for balance queries.
Now uses getCurrentRpcUrl() to respect user's network setting.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/mpc-system/services/service-party-app/src/pages/Home.tsx

@@ -8,6 +8,7 @@ import {
   isValidAddress,
   isValidAmount,
   getCurrentNetwork,
+  getCurrentRpcUrl,
   type PreparedTransaction,
 } from '../utils/transaction';
 
@@ -29,9 +30,6 @@ interface ShareWithAddress extends ShareItem {
   balanceLoading?: boolean;
 }
 
-// Kava Testnet EVM RPC endpoint
-const KAVA_TESTNET_RPC = 'https://evm.testnet.kava.io';
-
 /**
  * 获取 KAVA 代币余额
  * @param address EVM 地址
@@ -39,7 +37,8 @@ const KAVA_TESTNET_RPC = 'https://evm.testnet.kava.io';
  */
 async function fetchKavaBalance(address: string): Promise<string> {
   try {
-    const response = await fetch(KAVA_TESTNET_RPC, {
+    const rpcUrl = getCurrentRpcUrl();
+    const response = await fetch(rpcUrl, {
       method: 'POST',
       headers: { 'Content-Type': 'application/json' },
       body: JSON.stringify({