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.Tests/Gateway/Dashboard/DashboardCookieOptionsTests.cs

@@ -11,6 +11,7 @@ namespace ZB.MOM.WW.MxGateway.Tests.Gateway.Dashboard;
 public sealed class DashboardCookieOptionsTests
 {
     /// <summary>Verifies that the application configures secure dashboard authentication cookies.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Build_ConfiguresSecureDashboardCookie()
     {
@@ -36,6 +37,7 @@ public sealed class DashboardCookieOptionsTests
     /// relaxes the cookie to <see cref="CookieSecurePolicy.SameAsRequest"/> so
     /// the dashboard can be reached over plain HTTP in dev.
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Build_WithRequireHttpsCookieFalse_UsesSameAsRequest()
     {
@@ -55,6 +57,7 @@ public sealed class DashboardCookieOptionsTests
     /// cookie name, so a gateway instance sharing a hostname with another can be given a
     /// distinct name (browser cookies are scoped by host+path, not port).
     /// </summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task Build_WithCookieNameOverride_UsesConfiguredName()
     {