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/Dashboard/DashboardApiKeyAuthorization.cs

@@ -6,6 +6,7 @@ public sealed class DashboardApiKeyAuthorization
 {
     /// <summary>Determines whether the user can manage API keys.</summary>
     /// <param name="user">The authenticated user principal.</param>
+    /// <returns><see langword="true"/> if the user is authenticated and holds the <see cref="DashboardRoles.Admin"/> role; otherwise <see langword="false"/>.</returns>
     public bool CanManage(ClaimsPrincipal user)
     {
         if (user.Identity?.IsAuthenticated != true)