fix(@schematics/angular): set explicit type for the app-shell component

`ng generate app-shell` adds an `AppShell` import from `./app-shell/app-shell`, but the component it
generates inherits the workspace `type` option. In workspaces that set
`"@schematics/angular:component": { "type": "component" }`, such as those updated to v20, the
component was generated as `app-shell.component.ts` and the import failed to resolve.

(cherry picked from commit 0be52a8)

Author: MeAkib

packages/schematics/angular/app-shell/index.ts

@@ -210,6 +210,11 @@ const appShellSchematic: RuleFactory<AppShellOptions> = createProjectSchematic(
         module: 'app.module.server.ts',
         project: options.project,
         standalone: isStandalone,
+        // The `AppShell` import added above expects the default file path and a named export, so
+        // the component must not inherit a `type`, `flat` or `exportDefault` from the workspace.
+        type: '',
+        flat: false,
+        exportDefault: false,
       }),
     ]);
   },