fix(component): fix accessibility issue for post-breadcrumbs component (#6294)

## 📄 Description
This PR fixes accessibility issues in the post-breadcrumbs component by:
- Wrapping breadcrumb items in proper `<li>` elements for semantic HTML
structure
- Moving `aria-current="page"` attribute from the breadcrumb item to the
parent list item
- Updating CSS selectors to target the new DOM structure
(`li[aria-current="page"] post-breadcrumb-item`)

---

## 📝 Checklist

- ✅ My code follows the style guidelines of this project
- 🛠️ I have performed a self-review of my own code
- 📄 I have made corresponding changes to the documentation
- ⚠️ My changes generate no new warnings or errors
- 🧪 I have added tests that prove my fix is effective or that my feature
works
- ✔️ New and existing unit tests pass locally with my changes

Author: alionazherdetska

.changeset/green-crabs-talk.md

@@ -0,0 +1,5 @@
+---
+'@swisspost/design-system-components': patch
+---
+
+Fixed accessibility issue in the `<post-breadcrumbs>` component by wrapping breadcrumb items in `<li>` elements.

packages/components/src/components/post-breadcrumbs/post-breadcrumbs.scss

@@ -167,7 +167,7 @@ post-menu::part(popover-container) {
   }
 }
 
-post-breadcrumb-item:last-of-type {
+li[aria-current="page"] post-breadcrumb-item {
   pointer-events: none;
   color: tokens.get('breadcrumb-selected-fg');
   font-weight: tokens.get('breadcrumb-selected-font-weight');

packages/components/src/components/post-breadcrumbs/post-breadcrumbs.tsx

@@ -139,7 +139,7 @@ export class PostBreadcrumbs {
 
             {/* Conditionally render concatenated menu or individual breadcrumb items */}
             {this.isConcatenated ? (
-              <div
+              <li
                 role="none"
                 class="menu-trigger-wrapper"
                 onKeyDown={e => {
@@ -174,19 +174,23 @@ export class PostBreadcrumbs {
                     ))}
                   </post-menu>
                 </div>
-              </div>
+              </li>
             ) : (
               visibleItems.map(item => (
-                <post-breadcrumb-item url={item.url} key={item.url || item.text}>
-                  {item.text}
-                </post-breadcrumb-item>
+                <li>
+                  <post-breadcrumb-item url={item.url} key={item.url || item.text}>
+                    {item.text}
+                  </post-breadcrumb-item>
+                </li>
               ))
             )}
 
             {this.lastItem && (
-              <post-breadcrumb-item url={this.lastItem.url} aria-current="page" tabindex={-1}>
-                {this.lastItem.text}
-              </post-breadcrumb-item>
+              <li aria-current="page">
+                <post-breadcrumb-item url={this.lastItem.url} tabindex={-1}>
+                  {this.lastItem.text}
+                </post-breadcrumb-item>
+              </li>
             )}
           </ol>