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.

eslint.config.mjs

@@ -0,0 +1,4 @@
+// Nuxt generates the base flat config during `nuxt prepare`.
+import withNuxt from './.nuxt/eslint.config.mjs'
+
+export default withNuxt()