fix: add eth-account dependency for blockchain testing

- Add eth-account>=0.13.0 to pyproject.toml dependencies
- Add eth-account>=0.13.0 to central requirements.txt
- Fixes CI test failure: ModuleNotFoundError: No module named 'eth_account'
- Ensures blockchain contract tests can import eth_account properly
- Required for Guardian Contract and other blockchain functionality

requirements.txt

@@ -35,6 +35,7 @@ cryptography>=46.0.0
 ecdsa>=0.19.0
 base58>=2.1.1
 web3>=6.11.0
+eth-account>=0.13.0
 
 # Data Processing
 pandas>=2.2.0