feat(db): add SourceNode column to Notifications

src/ScadaLink.ConfigurationDatabase/Configurations/NotificationOutboxConfiguration.cs

@@ -47,10 +47,14 @@ public class NotificationOutboxConfiguration : IEntityTypeConfiguration<Notifica
 
         builder.Property(n => n.SourceScript).HasMaxLength(200);
 
-        // SourceNode (Audit Log #23, SourceNode-stamping): mapped in a follow-on migration
-        // (AddNotificationSourceNode). Ignored here for now so the AddAuditLogSourceNode
-        // migration only touches AuditLog. Removed in the AddNotificationSourceNode commit.
-        builder.Ignore(n => n.SourceNode);
+        // SourceNode (Audit Log #23, SourceNode-stamping): node-local identifier of the
+        // cluster member that produced the notification (e.g. "node-a", "central-a").
+        // NULL is valid for rows that pre-date this feature. ASCII — varchar(64).
+        // No index — KPIs are per-site on this table, not per-node; SourceNode is only
+        // echoed onto NotifyDeliver audit rows (#23) for cross-row correlation.
+        builder.Property(n => n.SourceNode)
+            .HasColumnType("varchar(64)")
+            .HasMaxLength(64);
 
         // OriginExecutionId (Audit Log #23): nullable uniqueidentifier carried from the
         // site so the dispatcher can echo it onto NotifyDeliver audit rows. No index —

src/ScadaLink.ConfigurationDatabase/Migrations/20260523201950_AddNotificationSourceNode.cs

@@ -0,0 +1,41 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ScadaLink.ConfigurationDatabase.Migrations
+{
+    /// <summary>
+    /// Adds the <c>SourceNode</c> column to the central <c>Notifications</c> table (#21,
+    /// SourceNode-stamping). <c>SourceNode</c> identifies the cluster node that produced the
+    /// notification (e.g. <c>node-a</c>, <c>central-a</c>) — ASCII-only, so <c>varchar(64)</c>
+    /// not <c>nvarchar</c>. <c>NULL</c> is valid for rows that pre-date this feature.
+    ///
+    /// The change is purely additive: <c>SourceNode varchar(64) NULL</c> is added with no
+    /// default, so the operation is a metadata-only <c>ALTER TABLE … ADD</c>. Unlike
+    /// <c>AuditLog</c>, the <c>Notifications</c> table is NOT partitioned, so a plain
+    /// <c>ADD</c> is fine. No index — Notification Outbox KPIs are per-site, not per-node,
+    /// on this table; <c>SourceNode</c> is only echoed onto <c>NotifyDeliver</c> audit rows
+    /// (#23) for cross-row correlation. Historical rows stay <c>NULL</c>.
+    /// </summary>
+    public partial class AddNotificationSourceNode : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "SourceNode",
+                table: "Notifications",
+                type: "varchar(64)",
+                maxLength: 64,
+                nullable: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "SourceNode",
+                table: "Notifications");
+        }
+    }
+}

src/ScadaLink.ConfigurationDatabase/Migrations/ScadaLinkDbContextModelSnapshot.cs

@@ -820,6 +820,10 @@ namespace ScadaLink.ConfigurationDatabase.Migrations
                         .HasMaxLength(200)
                         .HasColumnType("nvarchar(200)");
 
+                    b.Property<string>("SourceNode")
+                        .HasMaxLength(64)
+                        .HasColumnType("varchar(64)");
+
                     b.Property<string>("SourceScript")
                         .HasMaxLength(200)
                         .HasColumnType("nvarchar(200)");

tests/ScadaLink.ConfigurationDatabase.Tests/Migrations/AddNotificationSourceNodeMigrationTests.cs

@@ -0,0 +1,76 @@
+using Xunit;
+
+namespace ScadaLink.ConfigurationDatabase.Tests.Migrations;
+
+/// <summary>
+/// SourceNode-stamping (#23) integration tests for the
+/// <c>AddNotificationSourceNode</c> migration: applies the EF migrations to a
+/// freshly-created MSSQL test database on the running infra/mssql container and
+/// asserts that the central <c>Notifications</c> table carries the new
+/// <c>SourceNode varchar(64) NULL</c> column. No index — Notification Outbox KPIs
+/// are per-site, not per-node, so the column is never a query predicate on this
+/// table; it's only echoed onto NotifyDeliver audit rows (#23) for cross-row
+/// correlation.
+/// </summary>
+/// <remarks>
+/// <c>Notifications</c> is non-partitioned (operational state, not audit), so this
+/// is a plain metadata-only <c>ALTER TABLE … ADD</c> with no index.
+/// </remarks>
+public class AddNotificationSourceNodeMigrationTests : IClassFixture<MsSqlMigrationFixture>
+{
+    private readonly MsSqlMigrationFixture _fixture;
+
+    public AddNotificationSourceNodeMigrationTests(MsSqlMigrationFixture fixture)
+    {
+        _fixture = fixture;
+    }
+
+    [SkippableFact]
+    public async Task AppliesMigration_AddsSourceNodeColumn_ToNotifications()
+    {
+        Skip.IfNot(_fixture.Available, _fixture.SkipReason);
+
+        var present = await ScalarAsync<int>(
+            "SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS " +
+            "WHERE TABLE_NAME = 'Notifications' AND COLUMN_NAME = 'SourceNode' " +
+            "AND TABLE_SCHEMA = 'dbo';");
+        Assert.Equal(1, present);
+    }
+
+    [SkippableFact]
+    public async Task SourceNodeColumn_IsNullableVarchar64()
+    {
+        Skip.IfNot(_fixture.Available, _fixture.SkipReason);
+
+        // varchar(64), not nvarchar — SourceNode is ASCII (`node-a`, `central-a` etc.).
+        var dataType = await ScalarAsync<string?>(
+            "SELECT DATA_TYPE FROM INFORMATION_SCHEMA.COLUMNS " +
+            "WHERE TABLE_NAME = 'Notifications' AND COLUMN_NAME = 'SourceNode';");
+        Assert.Equal("varchar", dataType);
+
+        var maxLength = await ScalarAsync<int>(
+            "SELECT CHARACTER_MAXIMUM_LENGTH FROM INFORMATION_SCHEMA.COLUMNS " +
+            "WHERE TABLE_NAME = 'Notifications' AND COLUMN_NAME = 'SourceNode';");
+        Assert.Equal(64, maxLength);
+
+        var isNullable = await ScalarAsync<string?>(
+            "SELECT IS_NULLABLE FROM INFORMATION_SCHEMA.COLUMNS " +
+            "WHERE TABLE_NAME = 'Notifications' AND COLUMN_NAME = 'SourceNode';");
+        Assert.Equal("YES", isNullable);
+    }
+
+    // --- helpers ------------------------------------------------------------
+
+    private async Task<T> ScalarAsync<T>(string sql)
+    {
+        await using var conn = _fixture.OpenConnection();
+        await using var cmd = conn.CreateCommand();
+        cmd.CommandText = sql;
+        var result = await cmd.ExecuteScalarAsync();
+        if (result is null || result is DBNull)
+        {
+            return default!;
+        }
+        return (T)Convert.ChangeType(result, typeof(T) == typeof(string) ? typeof(string) : Nullable.GetUnderlyingType(typeof(T)) ?? typeof(T))!;
+    }
+}