Staking pallet lives on Asset Hub, not Relay Chain.
- RC HEZ staking set to null
- AH HEZ staking enabled with relaychain and nomination-pools
- AH externalApi staking subquery URL added
- Removed RC staking override from global configs
The staking dashboard was showing INACTIVE because all Pezkuwi chains
(including Asset Hub) were routed to the relay chain SubQuery for
staking stats. The relay SubQuery only has relay chain activeStakers,
not AH pool stash accounts. Split the override so Asset Hub queries
its own SubQuery endpoint which has the pool stash data.