refactor(configdb): drop ClusterNode.RedundancyRole (replaced by Akka leader)

Phase 1d of the v2 entity-model rewrite. The static RedundancyRole column
is replaced by Akka cluster's role-leader-of-"driver" election at runtime
(see RedundancyStateActor + ServiceLevelCalculator in Task 35).

Changes:

  - Removed `public required RedundancyRole RedundancyRole` from
    ClusterNode entity.
  - Removed `e.Property(x => x.RedundancyRole).HasConversion<string>()...`
    mapping from OtOpcUaConfigDbContext.ConfigureClusterNode.
  - Removed the `UX_ClusterNode_Primary_Per_Cluster` filtered unique index
    (filter referenced [RedundancyRole]='Primary').
  - Dropped `using ZB.MOM.WW.OtOpcUa.Configuration.Enums` from ClusterNode.cs
    (no longer needed).
  - Deleted `Enums/RedundancyRole.cs` — the enum is unused in v2-kept code.
  - DraftValidator: dropped the "exactly one Primary per cluster"
    validation block. Comment in place explaining v2 picks primary at
    runtime via Akka.
  - DraftValidatorTests: dropped ValidateClusterTopology_flags_multiple_Primary
    test; reworked BuildNode helper to no longer take a `role` argument.

Untouched (Server + Admin still reference RedundancyRole; accepted broken
per Task 56 policy):

  src/Server/ZB.MOM.WW.OtOpcUa.Server/Redundancy/{ClusterTopologyLoader,
    RedundancyStatePublisher, RedundancyTopology, ServiceLevelCalculator}.cs
  src/Server/ZB.MOM.WW.OtOpcUa.Admin/Services/RedundancyMetrics.cs

DB-runtime tests will fail against the new schema (Task 14f's migration
drops the column) — to be updated in Task 14f's SchemaComplianceTests
update:

  - SchemaComplianceTests.cs:55 (expected filtered index list)
  - StoredProceduresTests.cs:263 (raw INSERT names the column)

Verification:
  src/Core/ZB.MOM.WW.OtOpcUa.Configuration            -> 0 errors
  tests/Core/ZB.MOM.WW.OtOpcUa.Configuration.Tests    -> 0 errors
  whole solution                                       -> 71 errors
    (70 from Task 14b in Server/Admin, +1 new Server/Redundancy reference)

src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Entities/ClusterNode.cs

@@ -1,5 +1,3 @@
-using ZB.MOM.WW.OtOpcUa.Configuration.Enums;
-
 namespace ZB.MOM.WW.OtOpcUa.Configuration.Entities;
 
 /// <summary>Physical OPC UA server node within a <see cref="ServerCluster"/>.</summary>
@@ -10,8 +8,6 @@ public sealed class ClusterNode
 
     public required string ClusterId { get; set; }
 
-    public required RedundancyRole RedundancyRole { get; set; }
-
     /// <summary>Machine hostname / IP.</summary>
     public required string Host { get; set; }
 

src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Enums/RedundancyRole.cs

@@ -1,9 +0,0 @@
-namespace ZB.MOM.WW.OtOpcUa.Configuration.Enums;
-
-/// <summary>Per-node redundancy role within a cluster. Per decision #84.</summary>
-public enum RedundancyRole
-{
-    Primary,
-    Secondary,
-    Standalone,
-}

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

@@ -115,7 +115,6 @@ public sealed class OtOpcUaConfigDbContext(DbContextOptions<OtOpcUaConfigDbConte
             e.HasKey(x => x.NodeId);
             e.Property(x => x.NodeId).HasMaxLength(64);
             e.Property(x => x.ClusterId).HasMaxLength(64);
-            e.Property(x => x.RedundancyRole).HasConversion<string>().HasMaxLength(16);
             e.Property(x => x.Host).HasMaxLength(255);
             e.Property(x => x.ApplicationUri).HasMaxLength(256);
             e.Property(x => x.DriverConfigOverridesJson).HasColumnType("nvarchar(max)");
@@ -130,10 +129,10 @@ public sealed class OtOpcUaConfigDbContext(DbContextOptions<OtOpcUaConfigDbConte
             // Fleet-wide unique per decision #86
             e.HasIndex(x => x.ApplicationUri).IsUnique().HasDatabaseName("UX_ClusterNode_ApplicationUri");
             e.HasIndex(x => x.ClusterId).HasDatabaseName("IX_ClusterNode_ClusterId");
-            // At most one Primary per cluster
-            e.HasIndex(x => x.ClusterId).IsUnique()
-                .HasFilter("[RedundancyRole] = 'Primary'")
-                .HasDatabaseName("UX_ClusterNode_Primary_Per_Cluster");
+            // v2: the "one Primary per cluster" filtered unique index (and the RedundancyRole
+            // column it filtered on) are gone. Akka cluster leader-of-driver-role is the
+            // authoritative primary signal (see RedundancyStateActor + ServiceLevelCalculator,
+            // Task 35).
         });
     }
 

src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Validation/DraftValidator.cs

@@ -228,14 +228,9 @@ public static class DraftValidator
                 $"Toggle the missing node(s) back on or change RedundancyMode/NodeCount to match.",
                 cluster.ClusterId));
 
-        // Primary uniqueness — decision #84. Two Primary nodes is always an invariant violation
-        // regardless of mode; catch it here so publish fails loud rather than the runtime
-        // demoting both to ServiceLevelBand.InvalidTopology at boot.
-        var primaryCount = clusterNodes.Count(n => n.Enabled && n.RedundancyRole == RedundancyRole.Primary);
-        if (primaryCount > 1)
-            errors.Add(new("ClusterMultiplePrimary",
-                $"Cluster '{cluster.ClusterId}' has {primaryCount} Enabled Primary nodes. At most one Primary per cluster.",
-                cluster.ClusterId));
+        // v2: the v1 "exactly one Primary per cluster" invariant is gone. RedundancyRole was
+        // dropped in Task 14d; in v2 the Akka cluster's role-leader-of-"driver" elects the
+        // primary at runtime, so there is no static configuration to validate here.
 
         return errors;
     }

tests/Core/ZB.MOM.WW.OtOpcUa.Configuration.Tests/DraftValidatorTests.cs

@@ -161,7 +161,7 @@ public sealed class DraftValidatorTests
     {
         var cluster = BuildCluster(nodeCount: nodeCount, mode: mode);
         var nodes = Enumerable.Range(0, enabledNodes)
-            .Select(i => BuildNode($"n-{i}", enabled: true, role: i == 0 ? RedundancyRole.Primary : RedundancyRole.Secondary))
+            .Select(i => BuildNode($"n-{i}", enabled: true))
             .ToList();
 
         var errors = DraftValidator.ValidateClusterTopology(cluster, nodes);
@@ -175,33 +175,24 @@ public sealed class DraftValidatorTests
         var cluster = BuildCluster(nodeCount: 2, mode: RedundancyMode.Hot);
         var nodes = new[]
         {
-            BuildNode("primary", enabled: true,  role: RedundancyRole.Primary),
-            BuildNode("backup",  enabled: false, role: RedundancyRole.Secondary),
+            BuildNode("primary", enabled: true),
+            BuildNode("backup",  enabled: false),
         };
 
         var errors = DraftValidator.ValidateClusterTopology(cluster, nodes);
         errors.ShouldContain(e => e.Code == "ClusterEnabledNodeCountMismatch");
     }
 
-    [Fact]
-    public void ValidateClusterTopology_flags_multiple_Primary()
-    {
-        var cluster = BuildCluster(nodeCount: 2, mode: RedundancyMode.Hot);
-        var nodes = new[]
-        {
-            BuildNode("a", enabled: true, role: RedundancyRole.Primary),
-            BuildNode("b", enabled: true, role: RedundancyRole.Primary),
-        };
-
-        var errors = DraftValidator.ValidateClusterTopology(cluster, nodes);
-        errors.ShouldContain(e => e.Code == "ClusterMultiplePrimary");
-    }
+    // v2: the "exactly one Primary per cluster" check is gone — Akka cluster's
+    // role-leader-of-"driver" elects the primary at runtime. The corresponding
+    // ValidateClusterTopology_flags_multiple_Primary test (and the
+    // ClusterMultiplePrimary error code it asserted) were removed alongside Task 14d.
 
     [Fact]
     public void ValidateClusterTopology_returns_no_errors_on_valid_standalone()
     {
         var cluster = BuildCluster(nodeCount: 1, mode: RedundancyMode.None);
-        var nodes = new[] { BuildNode("only", enabled: true, role: RedundancyRole.Primary) };
+        var nodes = new[] { BuildNode("only", enabled: true) };
 
         var errors = DraftValidator.ValidateClusterTopology(cluster, nodes);
         errors.ShouldBeEmpty();
@@ -219,11 +210,10 @@ public sealed class DraftValidatorTests
         CreatedBy = "t",
     };
 
-    private static ClusterNode BuildNode(string id, bool enabled, RedundancyRole role) => new()
+    private static ClusterNode BuildNode(string id, bool enabled) => new()
     {
         NodeId = id,
         ClusterId = "c-test",
-        RedundancyRole = role,
         Host = "localhost",
         OpcUaPort = 4840,
         DashboardPort = 5001,