feat(sites): record the artifact revision last deployed to a site

Site.ArtifactRevisionHash / ArtifactsDeployedAt (nullable, migration
AddSiteArtifactRevision) so the Sites page can tell whether a site's
system-wide artifacts are current. Not transported. Adds the
GetDeployedRevisionHashesAsync projection for the fleet-wide staleness batch.

Claude-Session: https://claude.ai/code/session_01Y5ef34iUUMjmwnMpL9xgmB

tests/ZB.MOM.WW.ScadaBridge.Transport.IntegrationTests/RoundTripEquivalenceTests.cs

@@ -45,8 +45,10 @@ namespace ZB.MOM.WW.ScadaBridge.Transport.IntegrationTests;
 /// Tasks 3–5. Excluded properties are limited to: surrogate <c>Id</c>s, FK id
 /// columns that are legitimately remapped to the target's own surrogate keys,
 /// inheritance-placeholder flags that are re-derived at import (never carried), and
-/// the one documented design reset (imported <see cref="Instance.State"/> →
-/// <see cref="InstanceState.NotDeployed"/>). Each exclusion is annotated inline.
+/// the documented design resets — imported <see cref="Instance.State"/> →
+/// <see cref="InstanceState.NotDeployed"/>, and <see cref="Site.ArtifactRevisionHash"/> /
+/// <see cref="Site.ArtifactsDeployedAt"/> → null ("artifacts never deployed" in the importing
+/// environment). Each exclusion is annotated inline.
 /// </para>
 /// <para>
 /// Both the "source" and "imported" entities are re-read from the DB (AsNoTracking)
@@ -783,6 +785,10 @@ public sealed class RoundTripEquivalenceTests : IDisposable
                 NodeBAddress = "akka://site@10.0.0.2:2552",
                 GrpcNodeAAddress = "10.0.0.1:8083",
                 GrpcNodeBAddress = "10.0.0.2:8083",
+                // Non-default deploy state, so the imported site is provably reset rather than
+                // accidentally equal to an unset source.
+                ArtifactRevisionHash = "artifact-hash-1",
+                ArtifactsDeployedAt = new DateTimeOffset(2026, 9, 14, 10, 0, 0, TimeSpan.Zero),
             };
             ctx.Sites.Add(site);
             await ctx.SaveChangesAsync();
@@ -883,8 +889,14 @@ public sealed class RoundTripEquivalenceTests : IDisposable
             var impConn = await ctx.DataConnections.AsNoTracking().SingleAsync(c => c.Name == "OpcUaPrimary");
             var impInstance = await LoadInstanceAsync(ctx, "Pump-01");
 
-            // Site.
-            AssertRoundTripEqual(srcSite, impSite, nameof(Site.Id));
+            // Site. ArtifactRevisionHash/ArtifactsDeployedAt are environment-specific deploy state
+            // (like Instance.State) — a site reads "artifacts never deployed" in the importing
+            // environment until artifacts are deployed there, so they are deliberately not
+            // transported.
+            AssertRoundTripEqual(srcSite, impSite,
+                nameof(Site.Id), nameof(Site.ArtifactRevisionHash), nameof(Site.ArtifactsDeployedAt));
+            Assert.Null(impSite.ArtifactRevisionHash);
+            Assert.Null(impSite.ArtifactsDeployedAt);
 
             // DataConnection. SiteId remapped; Primary/Backup config ride the SecretsBlock.
             AssertRoundTripEqual(srcConn, impConn, nameof(DataConnection.Id), nameof(DataConnection.SiteId));