fix: update xtzevm testnet chain ID to shadownet (127823)

The Etherlink testnet migrated from the deprecated ghostnet (chain ID 128123)
to the new shadownet testnet (chain ID 127823).

Fixes: CECHO-864

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: manojkumar138

config/chainIds.ts

@@ -107,7 +107,7 @@ export const CHAIN_IDS = {
   OKB_TESTNET: 1952,
   ZKSYNCERA_TESTNET: 300,
   ARCUSDC_TESTNET: 5042002,
-  XTZEVM_TESTNET: 128123,
+  XTZEVM_TESTNET: 127823,
   MORPHETH_TESTNET: 2910,
   CHILIZ_TESTNET: 88882,
   UNICHAIN_TESTNET: 1301,