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.CentralUI/Audit/AuditExportEndpoints.cs

@@ -61,6 +61,7 @@ public static class AuditExportEndpoints
     /// </summary>
     /// <param name="context">The HTTP context for the current request.</param>
     /// <param name="exportService">The export service used to stream audit rows as CSV.</param>
+    /// <returns>A task representing the asynchronous export streaming operation.</returns>
     internal static async Task HandleExportAsync(HttpContext context, IAuditLogExportService exportService)
     {
         var filter = ParseFilter(context.Request.Query);
@@ -94,6 +95,7 @@ public static class AuditExportEndpoints
     /// its own CLI / UI URL builder — so do NOT "fix" the two to one key name.
     /// </remarks>
     /// <param name="query">The query string parameters from the HTTP request.</param>
+    /// <returns>An <see cref="AuditLogQueryFilter"/> populated from the query string values.</returns>
     internal static AuditLogQueryFilter ParseFilter(IQueryCollection query)
     {
         var channels = AuditQueryParamParsers.ParseEnumList<AuditChannel>(query["channel"]);