fix: commit balance changes immediately after state transition and remove sender fallback for 'to' field

Changed transaction failure logging from warning to error level in PoA proposer.
Added immediate session.commit() after successful state transition to persist balance changes.
Removed fallback to sender address for 'to' field in submit_transaction as it should be required.

apps/blockchain-node/src/aitbc_chain/consensus/poa.py

@@ -283,9 +283,13 @@ class PoAProposer:
                     )
                     
                     if not success:
-                        self._logger.warning(f"[PROPOSE] Failed to apply transaction {tx.tx_hash}: {error_msg}")
+                        self._logger.error(f"[PROPOSE] Failed to apply transaction {tx.tx_hash}: {error_msg}")
                         continue
 
+                    # Commit the balance changes immediately after successful state transition
+                    session.commit()
+                    self._logger.info(f"[PROPOSE] Committed balance changes for tx {tx.tx_hash}")
+
                     # Check if transaction already exists in database
                     existing_tx = session.exec(
                         select(Transaction).where(

apps/blockchain-node/src/aitbc_chain/rpc/router.py

@@ -299,7 +299,7 @@ async def submit_transaction(tx_data: TransactionRequest) -> Dict[str, Any]:
         # _normalize_transaction_data expects "from", not "sender"
         tx_data_dict = {
             "from": tx_data.sender,
-            "to": tx_data.payload.get("to", tx_data.sender),  # Get to from payload or default to sender
+            "to": tx_data.payload.get("to"),  # Get to from payload (required field)
             "amount": tx_data.payload.get("amount", 0),  # Get amount from payload
             "fee": tx_data.fee,
             "nonce": tx_data.nonce,