fix(op-service/sources): use Prague-aware BlobBaseFee in headerInfo

headerInfo.BlobBaseFee() was still calling eth.CalcBlobFeeCancun() with
the raw excessBlobGas value, ignoring the RequestsHash field populated
from post-Pectra L1 RPC responses. With Sepolia excessBlobGas ~188-194M,
the Cancun formula (UpdateFraction=3338477) produces ~10^24 wei instead
of the correct ~10^16 wei from the Prague formula (UpdateFraction=5007716).

This is the actual dispatch target when l1_block_info.go calls
block.BlobBaseFee() — the concrete type returned by EthClient.InfoByHash
is *headerInfo (sources/types.go), not *headerBlockInfo (eth/block_info.go).
The prior fix (07c68f9) changed the call site but not the implementation.

CalcBlobFeeDefault detects Prague blocks via header.RequestsHash != nil,
which is correctly populated from the Alchemy Sepolia RPC response.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: claude

op-service/sources/types.go

@@ -74,7 +74,7 @@ func (h headerInfo) BlobBaseFee() *big.Int {
 	if h.Header.ExcessBlobGas == nil {
 		return nil
 	}
-	return eth.CalcBlobFeeCancun(*h.Header.ExcessBlobGas)
+	return eth.CalcBlobFeeDefault(h.Header)
 }
 
 func (h headerInfo) ExcessBlobGas() *uint64 {