refactor: Shared Links als Card-Grid mit Card-Menü (wie Cronjobs)

- index.html: shared-links-list → card-grid
- dashboard.js: Cards mit card-compact, card-menu-dropdown, fa-cog statt fa-robot
- dashboard.css: 60 Zeilen shared-link-*/danger-icon CSS entfernt (nutzt card-Styles)

wwwroot/index.html

@@ -84,7 +84,7 @@
         <div class="section-header">
           <h2>Geteilte Links</h2>
         </div>
-        <div class="shared-links-list" id="sharedLinksList"></div>
+        <div class="card-grid" id="sharedLinksCards"></div>
       </section>
     </div>
   </div>