Add OnFinality as a second RPC node for Aleph Zero, enable failover

Aleph Zero was configured with a single node (wss://ws.azero.dev,
the Foundation's own endpoint) and no nodeSelectionStrategy, so any
outage there fails the chain outright with no fallback - confirmed
live via direct curl (502 Bad Gateway from the endpoint's own nginx,
backend unreachable), which is what was timing out
BalancesIntegrationTest.testBalancesLoading/testFeeLoading[Aleph Zero]
in wallet-android CI. Aleph Zero itself is healthy and active (live
Foundation site/explorer, active aleph-node development, OnFinality/
Dwellir both offer public RPC for it) - this was a config gap, not a
dead chain. Added OnFinality's public endpoint as a second node with
roundRobin selection, matching the pattern already used for our own
Pezkuwi chain's 2-node setup.

chains/v22/android/chains.json

@@ -5154,10 +5154,15 @@
         }
       }
     ],
+    "nodeSelectionStrategy": "roundRobin",
     "nodes": [
       {
         "url": "wss://ws.azero.dev",
         "name": "Aleph Zero node"
+      },
+      {
+        "url": "wss://aleph-zero.api.onfinality.io/public-ws",
+        "name": "OnFinality"
       }
     ],
     "explorers": [