feat(config): add ClusterNode.AkkaPort/GrpcPort — central's dial targets

Per-cluster mesh Phase 1 groundwork. Once the meshes split (Phase 2) central
can no longer see a site node's appsettings, so the transport ports it must
dial have to live in a row central can read.

AkkaPort is non-nullable with a 4053 default — every node listens on a
remoting port, so 0 is never a truthful value and pre-existing rows must
migrate to something real. GrpcPort is nullable with no default: nothing
listens on it until Phase 5, and a non-null default would assert a port that
does not exist.

Both are documented as central's dial targets rather than the node's own
binding config; the duplication against Cluster:Port is reconciled in Task 4.

The new SchemaCompliance test is red until the migration lands (Task 2).

Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW

src/Core/ZB.MOM.WW.OtOpcUa.Configuration/OtOpcUaConfigDbContext.cs

@@ -142,6 +142,11 @@ public sealed class OtOpcUaConfigDbContext(DbContextOptions<OtOpcUaConfigDbConte
             e.Property(x => x.Host).HasMaxLength(255);
             e.Property(x => x.ApplicationUri).HasMaxLength(256);
             e.Property(x => x.DriverConfigOverridesJson).HasColumnType("nvarchar(max)");
+            // Central's dial targets (per-cluster mesh Phase 1). AkkaPort carries a DB-side default so
+            // rows migrated from before the column existed come out at 4053 rather than 0 — every node
+            // in the fleet does listen on a remoting port, so 0 is never a truthful value for it.
+            // GrpcPort has no default: nothing listens on it until Phase 5.
+            e.Property(x => x.AkkaPort).HasDefaultValue(4053);
             e.Property(x => x.LastSeenAt).HasColumnType("datetime2(3)");
             e.Property(x => x.CreatedAt).HasColumnType("datetime2(3)").HasDefaultValueSql("SYSUTCDATETIME()");
             e.Property(x => x.CreatedBy).HasMaxLength(128);