How to make archiver walk back to genesis block?

```
# ./blob-archiver --l1-beacon-http http://127.0.0.1:3500 --data-store file --file-directory /mnt/fast2/BLOBS --archiver-origin-block 0
t=2024-11-01T15:47:42+0000 lvl=crit msg="Application failed" message="failed to setup: invalid CLI flags: invalid origin block 0x0000000000000000000000000000000000000000000000000000000000000000"
```

Reproduce the failure with the shown blob-archiver command and the --archiver-origin-block 0 flag. Trace the CLI flag validation and origin-block handling to determine whether genesis traversal is supported; done should be a clear, working way to start from the genesis block or an explicit documented limitation.

Written by the indexing model from the issue text.