refactor(auditlog): consolidate SiteCall DTO mapper into Communication

Extract the verbatim-duplicated SiteCallOperationalDto -> SiteCall mapper
into a single public SiteCallDtoMapper static class in
ScadaLink.Communication.Grpc, mirroring AuditEventDtoMapper. Replaces three
identical private copies (SiteStreamGrpcServer.MapSiteCallFromDto,
ClusterClientSiteAuditClient.MapSiteCall, and the test-infra
DirectActorSiteStreamAuditClient.MapSiteCallFromDto), removes the now-stale
doc comment that justified the duplication, and drops the using directives
that became unused. Adds SiteCallDtoMapperTests for field-by-field coverage.

Only the FromDto direction is provided: nothing maps SiteCall back onto the
wire, so a ToDto would be dead code.

tests/ScadaLink.Communication.Tests/SiteCallDtoMapperTests.cs

@@ -0,0 +1,135 @@
+using Google.Protobuf.WellKnownTypes;
+using ScadaLink.Communication.Grpc;
+
+namespace ScadaLink.Communication.Tests;
+
+/// <summary>
+/// Field-coverage + edge tests for the <see cref="SiteCallDtoMapper"/> that
+/// decodes <see cref="SiteCallOperationalDto"/> (proto) into the
+/// <see cref="ScadaLink.Commons.Entities.Audit.SiteCall"/> persistence entity.
+/// Only the DTO→entity direction exists — nothing in the system maps a
+/// <c>SiteCall</c> back onto the wire — so there is no round-trip test.
+/// <c>IngestedAtUtc</c> is a site-side placeholder the central ingest actor
+/// overwrites, so it is asserted as "recent UTC" rather than a fixed value.
+/// </summary>
+public class SiteCallDtoMapperTests
+{
+    [Fact]
+    public void FromDto_FullyPopulated_MapsEveryField()
+    {
+        var trackedOperationId = Guid.NewGuid();
+        var createdAt = new DateTime(2026, 5, 20, 10, 0, 0, DateTimeKind.Utc);
+        var updatedAt = new DateTime(2026, 5, 20, 10, 5, 0, DateTimeKind.Utc);
+        var terminalAt = new DateTime(2026, 5, 20, 10, 10, 0, DateTimeKind.Utc);
+
+        var dto = new SiteCallOperationalDto
+        {
+            TrackedOperationId = trackedOperationId.ToString(),
+            Channel = "ApiOutbound",
+            Target = "ERP.GetOrder",
+            SourceSite = "site-melbourne",
+            Status = "Delivered",
+            RetryCount = 3,
+            LastError = "transient 503",
+            HttpStatus = 200,
+            CreatedAtUtc = Timestamp.FromDateTime(createdAt),
+            UpdatedAtUtc = Timestamp.FromDateTime(updatedAt),
+            TerminalAtUtc = Timestamp.FromDateTime(terminalAt),
+        };
+
+        var entity = SiteCallDtoMapper.FromDto(dto);
+
+        Assert.Equal(trackedOperationId, entity.TrackedOperationId.Value);
+        Assert.Equal("ApiOutbound", entity.Channel);
+        Assert.Equal("ERP.GetOrder", entity.Target);
+        Assert.Equal("site-melbourne", entity.SourceSite);
+        Assert.Equal("Delivered", entity.Status);
+        Assert.Equal(3, entity.RetryCount);
+        Assert.Equal("transient 503", entity.LastError);
+        Assert.Equal(200, entity.HttpStatus);
+        Assert.Equal(createdAt, entity.CreatedAtUtc);
+        Assert.Equal(updatedAt, entity.UpdatedAtUtc);
+        Assert.Equal(terminalAt, entity.TerminalAtUtc);
+    }
+
+    [Fact]
+    public void FromDto_EmptyLastError_BecomesNull()
+    {
+        var dto = NewMinimalDto();
+        dto.LastError = string.Empty;
+
+        var entity = SiteCallDtoMapper.FromDto(dto);
+
+        Assert.Null(entity.LastError);
+    }
+
+    [Fact]
+    public void FromDto_AbsentHttpStatus_StaysNull()
+    {
+        // Int32Value wrapper unset on the wire — preserves true null semantics
+        // for non-API cached writes.
+        var dto = NewMinimalDto();
+
+        Assert.Null(dto.HttpStatus);
+
+        var entity = SiteCallDtoMapper.FromDto(dto);
+
+        Assert.Null(entity.HttpStatus);
+    }
+
+    [Fact]
+    public void FromDto_AbsentTerminalAt_StaysNull()
+    {
+        // Timestamp wrapper unset while the call is still active.
+        var dto = NewMinimalDto();
+
+        Assert.Null(dto.TerminalAtUtc);
+
+        var entity = SiteCallDtoMapper.FromDto(dto);
+
+        Assert.Null(entity.TerminalAtUtc);
+    }
+
+    [Fact]
+    public void FromDto_Timestamps_RehydrateAsUtcKind()
+    {
+        var dto = NewMinimalDto();
+
+        var entity = SiteCallDtoMapper.FromDto(dto);
+
+        Assert.Equal(DateTimeKind.Utc, entity.CreatedAtUtc.Kind);
+        Assert.Equal(DateTimeKind.Utc, entity.UpdatedAtUtc.Kind);
+    }
+
+    [Fact]
+    public void FromDto_IngestedAtUtc_StampedAsRecentPlaceholder()
+    {
+        // IngestedAtUtc is a site-side DateTime.UtcNow placeholder; the central
+        // ingest actor overwrites it inside the dual-write transaction.
+        var before = DateTime.UtcNow;
+
+        var entity = SiteCallDtoMapper.FromDto(NewMinimalDto());
+
+        var after = DateTime.UtcNow;
+        Assert.InRange(entity.IngestedAtUtc, before, after);
+        Assert.Equal(DateTimeKind.Utc, entity.IngestedAtUtc.Kind);
+    }
+
+    [Fact]
+    public void FromDto_Null_Throws()
+    {
+        Assert.Throws<ArgumentNullException>(() => SiteCallDtoMapper.FromDto(null!));
+    }
+
+    private static SiteCallOperationalDto NewMinimalDto() => new()
+    {
+        TrackedOperationId = Guid.NewGuid().ToString(),
+        Channel = "DbOutbound",
+        Target = "warehouse.dbo.WriteOrder",
+        SourceSite = "site-brisbane",
+        Status = "Submitted",
+        RetryCount = 0,
+        CreatedAtUtc = Timestamp.FromDateTime(DateTime.UtcNow),
+        UpdatedAtUtc = Timestamp.FromDateTime(DateTime.UtcNow),
+    };
+}