DEV: Refactor isLastLink logic for header icon links

Move `isLastLink` logic to a method using `site.mobileView` service for
dynamic checks of visible links. This replaces static index comparisons
with runtime filtering, ensuring accurate detection in both mobile and
desktop views.

Improves maintainability and correctness of conditional styling for the
last custom header icon link.

Author: megothss

javascripts/discourse/initializers/initialize-for-header-icon-links.gjs

@@ -1,4 +1,5 @@
 import Component from "@glimmer/component";
+import { service } from "@ember/service";
 import { dasherize } from "@ember/string";
 import { htmlSafe } from "@ember/template";
 import concatClass from "discourse/helpers/concat-class";
@@ -27,13 +28,11 @@ export default {
       try {
         const links = settings.header_links || [];
 
-        links.forEach((link, index) => {
+        links.forEach((link) => {
           const iconTemplate = buildIconTemplate(link.icon, link.title);
           const className = `header-icon-${dasherize(link.title)}`;
           const target = link.target === "blank" ? "_blank" : "";
           const rel = link.target ? "noopener" : "";
-          const isLastLink =
-            index === links.length - 1 ? "last-custom-icon" : "";
 
           const numericWidth = Number(link.width);
           const style = Number.isFinite(numericWidth)
@@ -47,13 +46,25 @@ export default {
                 : link.view === "vdo" || link.view === "vdm";
             }
 
+            @service site;
+
+            get isLastLink() {
+              const visibleLinks = links.filter((item) =>
+                this.site.mobileView
+                  ? item.view === "vmo" || item.view === "vdm"
+                  : item.view === "vdo" || item.view === "vdm"
+              );
+
+              return link === visibleLinks.at(-1);
+            }
+
             <template>
               <li
                 class={{concatClass
                   "custom-header-icon-link"
                   className
                   link.view
-                  isLastLink
+                  (if this.isLastLink "last-custom-icon")
                 }}
               >
                 <a