debug: Add detailed logging to BlockchainClient for vote submission

Add logging at each stage:
- Context manager entry/exit
- submit_vote() method entry
- Validator selection
- HTTP request details
- Response handling

This will help identify exactly where the vote submission is failing.

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

e-voting-system/backend/blockchain_client.py

@@ -84,8 +84,11 @@ class BlockchainClient:
 
     async def __aenter__(self):
         """Async context manager entry"""
+        logger.info("[BlockchainClient.__aenter__] Creating AsyncClient")
         self._client = httpx.AsyncClient(timeout=self.timeout)
+        logger.info("[BlockchainClient.__aenter__] Refreshing validator status")
         await self.refresh_validator_status()
+        logger.info(f"[BlockchainClient.__aenter__] Ready with {len(self.healthy_validators)} healthy validators")
         return self
 
     async def __aexit__(self, exc_type, exc_val, exc_tb):
@@ -172,10 +175,16 @@ class BlockchainClient:
         Raises:
             Exception: If all validators are unreachable
         """
+        logger.info(f"[BlockchainClient.submit_vote] CALLED with voter_id={voter_id}, election_id={election_id}")
+        logger.info(f"[BlockchainClient.submit_vote] healthy_validators count: {len(self.healthy_validators)}")
+
         validator = self._get_healthy_validator()
         if not validator:
+            logger.error("[BlockchainClient.submit_vote] No healthy validators available!")
             raise Exception("No healthy validators available")
 
+        logger.info(f"[BlockchainClient.submit_vote] Selected validator: {validator.node_id}")
+
         # Generate transaction ID if not provided
         if not transaction_id:
             import uuid
@@ -215,17 +224,21 @@ class BlockchainClient:
             "id": transaction_id
         }
 
-        logger.info(f"Submitting vote to {validator.node_id}: tx_id={transaction_id}")
+        logger.info(f"[BlockchainClient.submit_vote] Submitting vote to {validator.node_id}: tx_id={transaction_id}")
+        logger.info(f"[BlockchainClient.submit_vote] RPC URL: {validator.rpc_url}/rpc")
 
         try:
             if not self._client:
+                logger.error("[BlockchainClient.submit_vote] AsyncClient not initialized!")
                 raise Exception("AsyncClient not initialized")
 
+            logger.info(f"[BlockchainClient.submit_vote] Sending POST request to {validator.rpc_url}/rpc")
             response = await self._client.post(
                 f"{validator.rpc_url}/rpc",
                 json=rpc_request,
                 timeout=self.timeout
             )
+            logger.info(f"[BlockchainClient.submit_vote] Response received: status={response.status_code}")
 
             response.raise_for_status()
             result = response.json()