consensus: improve block proposal timing and return status, fix transaction field mapping in sync

- Add initial sleep before first proposal to prevent immediate block creation
- Return bool from _propose_block to indicate if block was actually proposed
- Wait for next slot only after successful proposal, use regular interval after skipped proposals
- Add 1s sleep after proposal errors to prevent tight error loops
- Add parent_hash, proposer, and state_root fields to /rpc/blocks-range response
- Fix transaction field mapping

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

@@ -254,10 +254,13 @@ async def get_blocks_range(start: int = 0, end: int = 10, include_tx: bool = Tru
             block_data = {
                 "height": b.height,
                 "hash": b.hash,
+                "parent_hash": b.parent_hash,
+                "proposer": b.proposer,
                 "timestamp": b.timestamp.isoformat(),
                 "tx_count": b.tx_count,
+                "state_root": b.state_root,
             }
-            
+
             if include_tx:
                 # Fetch transactions for this block
                 txs = session.exec(