Plugins: add card extension to nav-landing-page (#113768)

* Plugins: add card extension to nav-landing-page

* feat(nav-landing-page): update card extension to include category and onClick support

* feat(NavLandingPage): add setPluginLinksHook to test setup

* feat(NavLandingPageCard): refactor className handling using cx for better style management

* feat(NavLandingPage): update card extension targets to use plural form for consistency

* feat(NavLandingPage): add warning for mutually exclusive extension points

e2e-playwright/test-plugins/grafana-extensionstest-app/module.tsx

@@ -78,6 +78,13 @@ export const plugin = new AppPlugin<{}>()
           return undefined;
       }
     },
+  })
+  .addLink({
+    targets: 'grafana/dynamic/nav-landing-page/nav-id-cfg/cards/v1',
+    title: 'Extensions Test App',
+    description: 'This card tests the admin page card extension point',
+    path: `/a/${pluginJson.id}/`,
+    category: 'error',
   });
 
 function isSupported(context?: PluginExtensionPanelContext): boolean {

e2e-playwright/test-plugins/grafana-extensionstest-app/plugin.json

@@ -55,6 +55,11 @@
         "targets": ["grafana/dashboard/panel/menu"],
         "title": "Open from time series or pie charts (onClick)",
         "description": "This link will only be visible on time series and pie charts"
+      },
+      {
+        "targets": ["grafana/dynamic/nav-landing-page/nav-id-cfg/cards/v1"],
+        "title": "Extensions Test App",
+        "description": "This card tests the admin page card extension point"
       }
     ],
     "extensionPoints": [