♻️ refactor(frontend): split HealthDashboard into smart wrapper + dumb View for state-based stories

User feedback (PR #32 commit, T13 follow-up): HealthDashboard.stories.ts could not
demonstrate Loading or Error states because the component used useFetch internally
and didn't accept props. Same limitation made unit-testing the rendering branches
impossible without mocking the Nuxt fetch layer.

Split into 2 files (SRP / DDD modular per code-reviewer skill):

- HealthDashboardView.vue (NEW): pure presentational, accepts data/pending/error
  as props. Adds explicit data-testid="health-loading" + "health-error" so e2e and
  unit tests can target each branch.
- HealthDashboard.vue (REFACTORED): now a thin smart wrapper that calls
  useFetch('/api/healthz') and forwards data/pending/error to HealthDashboardView.

Stories:
- HealthDashboardView.stories.ts (NEW): 4 stories — Healthy, Loading, ErrorState,
  HealthyHighUptime. Reviewers can now see all branches without running the backend.
- HealthDashboard.stories.ts: still has the Default story for the wrapper (smoke).

Tooling:
- shims-vue.d.ts: Vue file module declaration with permissive any-typing for the
  DefineComponent. Required because Vue 3 strict TS + Storybook propagates prop
  types poorly through .vue imports otherwise (false-positive TS2353 errors).

Backwards compatibility:
- pages/index.vue still imports <HealthDashboard /> (unchanged).
- All existing data-testid attributes preserved (health-dashboard, health-info,
  health-status). The new health-loading and health-error testids are additive.
- The Playwright tests from PR #32 continue to pass without modification.

🤖 Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/components/HealthDashboardView.vue

@@ -0,0 +1,30 @@
+<script setup lang="ts">
+export interface HealthInfo {
+  status: string
+  version: string
+  uptime_seconds: number
+  timestamp: string
+}
+
+defineProps<{
+  data: HealthInfo | null | undefined
+  pending: boolean
+  error: { message: string } | null | undefined
+}>()
+</script>
+
+<template>
+  <section data-testid="health-dashboard">
+    <h2>Server Health</h2>
+    <p v-if="pending" data-testid="health-loading">Loading...</p>
+    <p v-else-if="error" data-testid="health-error">
+      Error loading health: {{ error.message }}
+    </p>
+    <ul v-else-if="data" data-testid="health-info">
+      <li><strong>Status:</strong> <span data-testid="health-status">{{ data.status }}</span></li>
+      <li><strong>Version:</strong> {{ data.version }}</li>
+      <li><strong>Uptime:</strong> {{ data.uptime_seconds }} seconds</li>
+      <li><strong>Last check:</strong> {{ data.timestamp }}</li>
+    </ul>
+  </section>
+</template>