Email alert when blob missing from CL

[syntrust]

Fixes #480.

Reproduced by creating a new mainnet es-node and downloading blocks using --download.start 23935930 and --l1.beacon http://65.21.133.53:4200, as the blob at 23935934 was missing in 65.21.133.53.

ERROR[12-04|09:55:02.715] Did not find the event specified blob in the CL

This fix has been verified in the same environment with and without email configured.

Email example:

The downloader couldn't locate the specified blob in the consensus layer. The node is stopped pending resolution. Details from the EL event:
 - blockNumber: 23935934
 - kvIndex: 274
 - hash: 0x017d51be97d12e36e191e68f9873d0eccf89e7250a66eb2fe41b58cb14c761a2
This may indicate a potential issue with blob availability on the consensus layer.


Sent at: Fri, 05 Dec 2025 04:33:58 +0100

[ping-ke]

I don't think we need to lg.crit here, as it will cost es-node exit
func (l *logger) Crit(msg string, ctx ...interface{}) {
l.Write(LevelCrit, msg, ctx...)
os.Exit(1)
}

[syntrust]

This is precisely what is required by the issue. It is pointless to leave the node running in this situation, and the operator should be informed as soon as possible.