Snapshot metadata: fix empty height label, add state version and network upgrade

[nachog00]

The snapshot-golden workflow labels VolumeSnapshots with metadata, but:

1. Height is always empty — the metrics scrape for chain height isn't working, resulting in zcash-stack/height: "" on all labeled snapshots
2. Missing db state version — need zcash-stack/state-version (e.g. 27) so we know which zaino schema versions are compatible with the snapshot
3. Missing network upgrade — need zcash-stack/network-upgrade (e.g. NU6.2) so operators know which zebra versions can use the snapshot without forking

Current state of golden-mainnet zebra snapshots:

zebra-...-jcls2  height=?  zebra=?      db=?   2026-05-03  (pre-NU6.2, unlabeled)
zebra-...-4mtvm  height="" zebra=4.0.0  db=?   2026-05-03  (pre-NU6.2)
zebra-...-tq54f  height="" zebra=5.1.0  db=?   2026-06-11  (post-NU6.2)

This caused us to deploy pre-NU6.2 snapshots with post-NU6.2 zebras that then forked and corrupted state, requiring manual PVC restores.

Ideally we'd also have a listing command/script that presents snapshots with their metadata in a readable table.