consensus: integrate state root computation and validation with state transition system

- Add _compute_state_root helper function to compute Merkle Patricia Trie state root from account state
- Replace direct balance/nonce updates with state_transition.apply_transaction in block proposal
- Compute and set state_root for both regular blocks and genesis block
- Add state root verification in sync.py after importing blocks
- Add application-layer database validation with DatabaseOperationValidator class

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

@@ -8,11 +8,11 @@ from typing import Callable, ContextManager, Optional
 
 from sqlmodel import Session, select
 
-from ..logger import get_logger
-from ..metrics import metrics_registry
+from ..gossip import gossip_broker
+from ..state.merkle_patricia_trie import StateManager
+from ..state.state_transition import get_state_transition
 from ..config import ProposerConfig
 from ..models import Block, Account
-from ..gossip import gossip_broker
 
 _METRIC_KEY_SANITIZE = re.compile(r"[^a-zA-Z0-9_]")
 
@@ -22,6 +22,25 @@ def _sanitize_metric_suffix(value: str) -> str:
     return sanitized or "unknown"
 
 
+def _compute_state_root(session: Session, chain_id: str) -> str:
+    """Compute state root from current account state."""
+    state_manager = StateManager()
+    
+    # Get all accounts for this chain
+    accounts = session.exec(
+        select(Account).where(Account.chain_id == chain_id)
+    ).all()
+    
+    # Convert to dictionary
+    account_dict = {acc.address: acc for acc in accounts}
+    
+    # Compute state root
+    root = state_manager.compute_state_root(account_dict)
+    
+    # Return as hex string
+    return '0x' + root.hex()
+
+
 
 import time
 
@@ -200,10 +219,22 @@ class PoAProposer:
                     else:
                         self._logger.info(f"[PROPOSE] Recipient account exists for {recipient}")
 
-                    # Update balances
-                    sender_account.balance -= total_cost
-                    sender_account.nonce += 1
-                    recipient_account.balance += value
+                    # Apply state transition through validated transaction
+                    state_transition = get_state_transition()
+                    tx_data = {
+                        "from": sender,
+                        "to": recipient,
+                        "value": value,
+                        "fee": fee,
+                        "nonce": sender_account.nonce
+                    }
+                    success, error_msg = state_transition.apply_transaction(
+                        session, self._config.chain_id, tx_data, tx.tx_hash
+                    )
+                    
+                    if not success:
+                        self._logger.warning(f"[PROPOSE] Failed to apply transaction {tx.tx_hash}: {error_msg}")
+                        continue
 
                     # Check if transaction already exists in database
                     existing_tx = session.exec(
@@ -256,7 +287,7 @@ class PoAProposer:
                 proposer=self._config.proposer_id,
                 timestamp=timestamp,
                 tx_count=len(processed_txs),
-                state_root=None,
+                state_root=_compute_state_root(session, self._config.chain_id),
             )
             session.add(block)
             session.commit()
@@ -327,7 +358,7 @@ class PoAProposer:
                 proposer="genesis",  # Use "genesis" as the proposer for genesis block to avoid hash conflicts
                 timestamp=timestamp,
                 tx_count=0,
-                state_root=None,
+                state_root=_compute_state_root(session, self._config.chain_id),
             )
             session.add(genesis)
             try: