docs: add missing XML doc comments across gateway, worker, and .NET client

Resolves 1113 documentation-completeness gaps flagged by CommentChecker
(MissingReturns, MissingInheritDoc, InheritDocMisused, MissingDoc,
MissingParam, RedundantInheritDoc) so the API surface is fully documented
and the analyzer scan is clean. Doc comments only; no code changes.

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

@@ -7,6 +7,7 @@ internal static class DashboardGalaxyProjector
 {
     /// <summary>Projects the cache entry to a dashboard Galaxy summary.</summary>
     /// <param name="entry">The Galaxy hierarchy cache entry.</param>
+    /// <returns>The precomputed <see cref="DashboardGalaxySummary"/> from the cache entry.</returns>
     public static DashboardGalaxySummary Project(GalaxyHierarchyCacheEntry entry)
     {
         return entry.DashboardSummary;