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/Auth/AuthEndpoints.cs

@@ -19,6 +19,7 @@ public static class AuthEndpoints
 {
     /// <summary>Registers the <c>/auth/login</c>, <c>/auth/logout</c>, and <c>/auth/ping</c> endpoints on the given route builder.</summary>
     /// <param name="endpoints">The route builder to add the endpoints to.</param>
+    /// <returns>The same <paramref name="endpoints"/> instance, for call chaining.</returns>
     public static IEndpointRouteBuilder MapAuthEndpoints(this IEndpointRouteBuilder endpoints)
     {
         endpoints.MapPost("/auth/login", async (HttpContext context) =>
@@ -198,6 +199,7 @@ public static class AuthEndpoints
     /// server-side. See CentralUI-020.
     /// </summary>
     /// <param name="context">The current HTTP context used to check authentication state and write the response.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     public static Task HandlePing(HttpContext context)
     {
         context.Response.StatusCode = context.User.Identity?.IsAuthenticated == true
@@ -219,6 +221,7 @@ public static class AuthEndpoints
     /// <see cref="AuthenticationProperties.AllowRefresh"/> is left unset (null)
     /// so the middleware is free to slide the expiry on activity.
     /// </summary>
+    /// <returns>An <see cref="AuthenticationProperties"/> instance with <see cref="AuthenticationProperties.IsPersistent"/> set to <c>true</c> and no fixed expiry.</returns>
     public static AuthenticationProperties BuildSignInProperties() => new()
     {
         IsPersistent = true