fix: use validated top-level fields in submit_transaction

- Use tx_data.sender and tx_data.recipient instead of reading from payload
- Use tx_data.amount instead of tx_data.payload.get('amount')
- Fixes 'transaction.to is required' error when CLI sends fields at top level
- Pydantic model already validates and aliases from/to to sender/recipient

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

@@ -89,10 +89,11 @@ async def submit_transaction(
         chain_id = get_chain_id(None)
 
         # Convert TransactionRequest to dict for normalization
+        # Use validated top-level fields instead of reading from payload
         tx_data_dict = {
             "from": tx_data.sender,
-            "to": tx_data.payload.get("to"),
-            "amount": tx_data.payload.get("amount", tx_data.payload.get("value", 0)),
+            "to": tx_data.recipient,
+            "amount": tx_data.amount,
             "fee": tx_data.fee,
             "nonce": tx_data.nonce,
             "payload": tx_data.payload,