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.Communication/Grpc/SiteCallDtoMapper.cs

@@ -46,6 +46,7 @@ public static class SiteCallDtoMapper
     /// share one instant. The value sent on the wire is informational only.
     /// </remarks>
     /// <param name="dto">The wire-format site call DTO to map.</param>
+    /// <returns>A <see cref="SiteCall"/> entity populated from the DTO fields.</returns>
     public static SiteCall FromDto(SiteCallOperationalDto dto)
     {
         ArgumentNullException.ThrowIfNull(dto);