docs(src): add missing XML docs and strip tracking-ID comments

Sweep of 203 source files resolving CommentChecker findings: add
<summary>/<param>/<returns>/<inheritdoc> where missing, and remove
resolved task/issue tracking markers (Tests-NNN, Worker-NNN, Server-NNN,
Task N) from code comments. Comment/doc-only — no logic changes.
Server+Tests build clean under TreatWarningsAsErrors.

src/ZB.MOM.WW.MxGateway.Server/Diagnostics/GatewayRequestLoggingMiddlewareExtensions.cs

@@ -19,6 +19,7 @@ public static class GatewayRequestLoggingMiddlewareExtensions
 
     /// <summary>Adds gateway request logging scope middleware that reads correlation headers and redacts sensitive data.</summary>
     /// <param name="app">Application builder.</param>
+    /// <returns>The same <see cref="IApplicationBuilder"/>, for chaining.</returns>
     public static IApplicationBuilder UseGatewayRequestLoggingScope(this IApplicationBuilder app)
     {
         ArgumentNullException.ThrowIfNull(app);