chore(docker-env2): replicate site-x's LocalDb, mirroring docker/ site-a (#116)

Unreplicated, the standby holds no deployed configs, data connections or
S&F buffer: a seeded active kill showed the survivor take over the cluster
in 28 s but load no instances and run no scripts. Dev-only sync key.

Claude-Session: https://claude.ai/code/session_01GT67ACmpMR7b9LGRPLijMi

docker-env2/site-x-node-a/appsettings.Site.json

@@ -77,7 +77,23 @@
   // outside the volume and were lost on every recreate.
   // Replication is opt-in and configured separately; absent = local-only.
   "LocalDb": {
-    "Path": "/app/data/site-localdb.db"
+    "Path": "/app/data/site-localdb.db",
+    // site-x is env2's REPLICATED pair (since 2026-11-13, ScadaBridge#116 seeded soak),
+    // mirroring docker/ site-a. Without it the standby holds no deployed configs, data
+    // connections or S&F buffer, so a failover brings up an EMPTY active node: the
+    // cluster recovers but data collection does not.
+    //
+    // This node is the initiator (dials the peer); the stream is bidirectional. Port
+    // 8083 is the existing site gRPC listener. The ApiKey must be IDENTICAL on both
+    // nodes (LocalDbSyncAuthInterceptor is fail-closed). Dev-only key, not a secret.
+    "Replication": {
+      "PeerAddress": "http://scadabridge-env2-site-x-b:8083",
+      "ApiKey": "dev-env2-site-x-localdb-sync-key",
+      // Same sizing as docker/site-a (see the rationale there).
+      "MaxBatchSize": 64,
+      "MaxOplogRows": 250000,
+      "MaxOplogAge": "2.00:00:00"
+    }
   },
   // arch-review remediation WP1.2: the site hot-path audit writer's SQLite file has no
   // default path (mirrors LocalDb:Path above) and StartupValidator now requires it for

docker-env2/site-x-node-b/appsettings.Site.json

@@ -77,7 +77,16 @@
   // outside the volume and were lost on every recreate.
   // Replication is opt-in and configured separately; absent = local-only.
   "LocalDb": {
-    "Path": "/app/data/site-localdb.db"
+    "Path": "/app/data/site-localdb.db",
+    // The PASSIVE half of env2 site-x's replicated pair (see node-a): no PeerAddress,
+    // node-a dials in, and this node's writes still reach node-a over the same stream.
+    // The key MUST match node-a's exactly. Dev-only key, not a secret.
+    "Replication": {
+      "ApiKey": "dev-env2-site-x-localdb-sync-key",
+      "MaxBatchSize": 64,
+      "MaxOplogRows": 250000,
+      "MaxOplogAge": "2.00:00:00"
+    }
   },
   // arch-review remediation WP1.2: the site hot-path audit writer's SQLite file has no
   // default path (mirrors LocalDb:Path above) and StartupValidator now requires it for