✨ feat(frontend): Storybook + auto-generated Playwright e2e docs with screenshots (#30)

Storybook 8 + Playwright JSON reporter + auto-generated markdown docs with embedded screenshots and breadcrumbs. Frontend PRs now reviewable from Gitea web UI. ~95% Mistral autonomous via ICM workspace, trainer commit/PR (Mistral hit turn limit).

Co-authored-by: Gabriel Radureau <arcodange@gmail.com>
Co-committed-by: Gabriel Radureau <arcodange@gmail.com>

frontend/tests/e2e/health.spec.ts

@@ -5,4 +5,5 @@ test('home page loads and shows server health info', async ({ page }) => {
   await expect(page.getByTestId('health-dashboard')).toBeVisible()
   const heading = page.getByRole('heading', { name: /dance-lessons-coach/i })
   await expect(heading).toBeVisible()
+  await page.screenshot({ path: 'tests/e2e/screenshots/home-page-loads-and-shows-server-health-info.png', fullPage: true })
 })