Aggiungi DX boilerplate.

- Makefile:
  - make dev (go run ./cmd/server)
  - make ui-build (cd ui-kit && npm i && npm run build)
  - make ui-dev (watch)
  - make test (go test ./...)
  - make db-reset (solo sqlite: rimuovi ./data/app.db)
  - make fmt (gofmt)

- docker-compose.yml:
  - postgres service (porta 5432)
  - env compatibile con DB_PG_DSN

- README.md:
  - Quickstart sqlite
  - Quickstart postgres (docker compose)
  - dove stanno templates public/private/admin
  - email in develop: ./data/emails
  - build UI kit