WP-00: project skeleton with three-level test harness

Cargo workspace (domain, application, infrastructure, api), axum health endpoint
with SPA fallback, Vue 3 + Tailwind frontend, Vitest, Playwright, Makefile,
Gitea Actions CI and README.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

frontend/e2e/smoke.spec.ts

@@ -0,0 +1,7 @@
+import { test, expect } from '@playwright/test'
+
+test('app loads and shows backend health', async ({ page }) => {
+  await page.goto('/')
+  await expect(page.getByText('SoftVisor Monitoring')).toBeVisible()
+  await expect(page.getByTestId('backend-status')).toContainText('ok')
+})