feat(chain_sync): add retry logic with exponential backoff for RPC connections and block imports

- Add retry mechanism with exponential backoff for block broadcast loop
- Implement max 5 retries with 2s base delay for RPC connection failures
- Reset retry count on successful connection
- Add 20s wait period after max retries before resetting counter
- Add retry logic for block import with 3 attempts and 1s base delay
- Handle non-200 HTTP responses as exceptions to trigger retries
- Improve error logging

apps/blockchain-node/src/aitbc_chain/config.py

@@ -36,6 +36,9 @@ class ChainSettings(BaseSettings):
 
     block_time_seconds: int = 2
 
+    # Block production toggle (set false on followers)
+    enable_block_production: bool = True
+
     # Block production limits
     max_block_size_bytes: int = 1_000_000  # 1 MB
     max_txs_per_block: int = 500