feat(v2): boot /v2/dashboard through OrganizerLayoutV2 + AppShellV2

Replaces the Task 3 stub in pages-v2/dashboard.vue with the boot-proof
page (data-testid v2-dashboard, correct definePage meta). Adds the
Playwright CT smoke (appshell-boot.spec.ts) that mounts AppShellV2 in
Chromium and asserts both the shell root and slot content are visible;
uses page scope for the root-element assertion (CT component locator
only matches descendants, not the root itself). Full Plan-1 gate green:
typecheck 0 new errors, eslint clean, 5 vitest files / 21 tests + 2
component tests, vite build succeeded, typed-router has v2-dashboard.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/app/src/pages-v2/dashboard.vue

@@ -1,9 +1,17 @@
 <script setup lang="ts">
+// First v2 page — boot proof (RFC-WS-GUI-REDESIGN Plan 1). `public`
+// keeps it reachable without auth wiring during the foundation slice;
+// it is removed when the real dashboard lands in a later plan.
 definePage({ meta: { layout: 'OrganizerLayoutV2', public: true } })
 </script>
 
 <template>
-  <div data-testid="v2-dashboard-placeholder">
-    v2 dashboard
-  </div>
+  <section data-testid="v2-dashboard">
+    <h1 class="text-xl font-semibold text-surface-900 dark:text-surface-0">
+      v2 foundation OK
+    </h1>
+    <p class="mt-2 text-surface-600 dark:text-surface-300">
+      AppShellV2 skeleton renders this route at /v2/dashboard.
+    </p>
+  </section>
 </template>