rename: prefix gateway projects/namespaces with ZB.MOM.WW + sln→slnx

Apply the ZB.MOM.WW. prefix to all gateway-side projects, folders,
.csproj/.sln contents, C# namespaces, using directives, generated proto
C# (csharp_namespace + checked-in generated files), InternalsVisibleTo
attributes, project-name string literals (LoadProject, .sln lookups,
worker exe paths, staticwebassets manifest), and the install/script/doc
references that point at any of the above. Migrate the solution from
.sln to .slnx via `dotnet sln migrate` and delete the old file.

External-runtime identifiers are intentionally NOT prefixed so external
configuration keeps working:
- GatewayMetrics.cs MeterName ("MxGateway.Server")
- DashboardAuthenticationDefaults Scheme/Policy ("MxGateway.Dashboard")
- GatewayRequestLoggingMiddleware logger category ("MxGateway.Request")
- StaRuntime thread name ("MxGateway.Worker.STA")
- appsettings.json root section "MxGateway" + env-var prefix
  MxGateway__... and secret-name MxGateway:ApiKeyPepper
- C:\ProgramData\MxGateway\ data dir paths

Also fixes two tests that were not rename-related but became visible
while validating the rename:

- WorkerLiveMxAccessSmokeTests.ShutDownAsync: cancellation that the
  gateway service correctly maps to RpcException(Cancelled) per gRPC
  convention was being misclassified as a stream fault. Added a sibling
  catch on RpcException with StatusCode.Cancelled.

- IntegrationTestEnvironment.ResolveRepositoryRoot: extracted IsRepositoryRoot
  and made it accept either a .git marker OR a .sln/.slnx next to src/
  so the worker-exe walker works in non-git working copies.

clients/proto/proto-inputs.json's protoRoot updated to point at
src/ZB.MOM.WW.MxGateway.Contracts/Protos.

Verified by `dotnet build` and a full `dotnet test` of the .slnx with
MXGATEWAY_RUN_LIVE_{MXACCESS,LDAP,GALAXY}_TESTS=1:
  Tests: 472/472 pass
  Worker.Tests: 280/280 pass (4 dev-rig [Fact(Skip=...)] skipped)
  IntegrationTests: 18/18 pass

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardGalaxySummary.cs

@@ -0,0 +1,48 @@
+namespace ZB.MOM.WW.MxGateway.Server.Dashboard;
+
+/// <summary>
+///     Snapshot of the Galaxy Repository (ZB) browse state surfaced on the dashboard.
+///     Populated by <see cref="GalaxySummaryCache"/> on a background refresh cadence so
+///     the dashboard never blocks on SQL.
+/// </summary>
+public sealed record DashboardGalaxySummary(
+    DashboardGalaxyStatus Status,
+    DateTimeOffset? LastQueriedAt,
+    DateTimeOffset? LastSuccessAt,
+    DateTimeOffset? LastDeployTime,
+    string? LastError,
+    int ObjectCount,
+    int AreaCount,
+    int AttributeCount,
+    int HistorizedAttributeCount,
+    int AlarmAttributeCount,
+    IReadOnlyList<DashboardGalaxyTemplateUsage> TopTemplates,
+    IReadOnlyList<DashboardGalaxyCategoryCount> ObjectCategories)
+{
+    /// <summary>Gets the unknown Galaxy status placeholder.</summary>
+    public static DashboardGalaxySummary Unknown { get; } = new(
+        DashboardGalaxyStatus.Unknown,
+        LastQueriedAt: null,
+        LastSuccessAt: null,
+        LastDeployTime: null,
+        LastError: null,
+        ObjectCount: 0,
+        AreaCount: 0,
+        AttributeCount: 0,
+        HistorizedAttributeCount: 0,
+        AlarmAttributeCount: 0,
+        TopTemplates: Array.Empty<DashboardGalaxyTemplateUsage>(),
+        ObjectCategories: Array.Empty<DashboardGalaxyCategoryCount>());
+}
+
+public enum DashboardGalaxyStatus
+{
+    Unknown = 0,
+    Healthy = 1,
+    Stale = 2,
+    Unavailable = 3,
+}
+
+public sealed record DashboardGalaxyTemplateUsage(string TemplateName, int InstanceCount);
+
+public sealed record DashboardGalaxyCategoryCount(int CategoryId, string CategoryName, int ObjectCount);