fix(storybook): register v2-dashboard route so AppSidebar stories render

The story router only knew the pre-v2 route names, so SidebarNav's RouterLink
to the v2-prefixed 'v2-dashboard' threw 'No match for' and the Storybook error
boundary replaced every AppSidebar story. Add 'v2-dashboard' to the story
router's known names.

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

apps/app/.storybook/preview.ts

@@ -15,6 +15,9 @@ const routeNames = [
   'organisation-companies', 'organisation-form-failures',
   'organisation-settings', 'platform', 'platform-organisations',
   'platform-users', 'platform-form-failures', 'platform-activity-log',
+  // v2 shell nav targets (APP_NAVIGATION uses v2-prefixed route names) —
+  // without these, AppSidebar/SidebarNav RouterLinks throw "No match for".
+  'v2-dashboard',
 ]
 
 export const storyRouter = createRouter({