chore(docker): set NodeName on all 8 cluster nodes

Adds "NodeName" to the ScadaLink:Node section of each per-node
appsettings:
- central-a, central-b for the two central nodes
- node-a, node-b under each of the three sites (site-a, site-b, site-c)

After this commit + a redeploy, every fresh AuditLog / Notifications /
SiteCalls row gets stamped with the originating node's role name via
INodeIdentityProvider, satisfying the design's SourceNode invariant
end-to-end.

docker/central-node-a/appsettings.Central.json

@@ -2,6 +2,7 @@
   "ScadaLink": {
     "Node": {
       "Role": "Central",
+      "NodeName": "central-a",
       "NodeHostname": "scadalink-central-a",
       "RemotingPort": 8081
     },