chore: scaffold Nuxt 4 app with Postgres, tooling and health route

Nuxt 4 (app/ structure) + TypeScript, ESLint, Vitest + @nuxt/test-utils,
Drizzle + pg, a /api/health route with a DB ping, and a dev docker-compose
(app + Postgres). Verified: pnpm test, lint, and build pass; the built
server answers /api/health.

app/app.vue

@@ -0,0 +1,4 @@
+<template>
+  <NuxtRouteAnnouncer />
+  <NuxtPage />
+</template>