fix(storybook): stub AccessStore in the shell story (fixes storybook-a11y red)

The header now injects AccessStore (→ MeAdapter → ApiClient) for its admin links.
f719676 stubbed that in the site-header story but missed shell.stories.ts, which
renders the header via ShellComponent — with only provideRouter it threw NG0201
(no ApiClient provider), failing the Shell smoke-test and turning storybook-a11y
red on CI (deterministic, not the local worker-contention timeouts). Stub
AccessStore there too (can() → false, no admin links).

Verified: full test-storybook suite single-worker now 60 suites / 170 tests green.
Lesson: when a shared component gains a service dep, every story that renders it —
directly OR via a parent template — needs the provider.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/shared/layout/shell/shell.stories.ts

@@ -1,12 +1,19 @@
 import type { Meta, StoryObj } from '@storybook/angular';
 import { applicationConfig } from '@storybook/angular';
 import { provideRouter } from '@angular/router';
+import { AccessStore } from '@shared/application/access.store';
 import { ShellComponent } from './shell.component';
 
 const meta: Meta<ShellComponent> = {
   title: 'Design System/Templates/Shell',
   component: ShellComponent,
-  decorators: [applicationConfig({ providers: [provideRouter([])] })],
+  // The persistent header injects AccessStore (for its capability-gated admin links);
+  // stub it so the story needs no HTTP/ApiClient. `can` false → no admin links.
+  decorators: [
+    applicationConfig({
+      providers: [provideRouter([]), { provide: AccessStore, useValue: { can: () => false } }],
+    }),
+  ],
 };
 export default meta;
 type Story = StoryObj<ShellComponent>;