docs: complete XML doc coverage (returns, summaries, inheritdoc)

Resolve all 622 issues flagged by the enhanced CommentChecker: add missing
<returns> tags (incl. the standard phrasing on non-generic Task methods),
add missing <summary> tags, and replace misused/redundant <inheritdoc/> on
members that override or implement nothing with real documentation.
Documentation-only — no behavior change; solution builds clean.

src/ZB.MOM.WW.ScadaBridge.AuditLog/Central/ISiteEnumerator.cs

@@ -23,6 +23,7 @@ public interface ISiteEnumerator
     /// — the actor calls this once per tick.
     /// </summary>
     /// <param name="ct">Cancellation token for the async enumeration.</param>
+    /// <returns>A task that resolves to the current set of site entries to poll on the next reconciliation tick.</returns>
     Task<IReadOnlyList<SiteEntry>> EnumerateAsync(CancellationToken ct = default);
 }