feat(consensus): implement transaction processing in PoA block proposer

- Process transactions from mempool during block proposal
- Update sender and recipient account balances
- Create transaction records with confirmed status
- Include transaction hashes in block hash computation
- Update tx_count in blocks based on processed transactions
- Add balance validation and nonce management
- Handle transaction failures gracefully with logging
- Fix get_balance endpoint to use chain_id helper
- Update

scripts/init_production_genesis.py

@@ -128,8 +128,8 @@ def main() -> None:
     if args.db_path:
         os.environ["DB_PATH"] = str(args.db_path)
 
-    from aitbc_chain.config import Settings
-    settings = Settings()
+    from aitbc_chain.config import ChainSettings
+    settings = ChainSettings()
 
     print(f"[*] Initializing database at {settings.db_path}")
     init_db()