chore: standardize on Yarn + Node 22.21.1 across CI, Docker, and README

[Copilot]

• Actualizar badge de Astro (5.15.3 → 5.16+)
• Agregar badge de Node 22.21.1, Yarn 1.22 y CI (GitHub Actions)
• Corregir enlace Demo a toallaalacarta.netlify.app (antes apuntaba a storeplate)
• Actualizar sección de dependencias como tabla con versiones mínimas
• Agregar nota sobre Yarn como gestor oficial (no usar npm)
• Agregar sección de variables de entorno con tabla de .env.example
• Traducir comandos al español (Install/Dev/Build/Preview)
• Agregar yarn preview como comando documentado
• Corregir "Reporting Issues" para apuntar al repo correcto (Medalcode/Toallaalacarta)

Original prompt

Estandarizar el repositorio en Yarn como único gestor de paquetes y alinear la versión de Node usada en CI/workflows/Docker/Netlify.

Repositorio: Medalcode/Toallaalacarta (default branch: main)

Cambios requeridos:

1. GitHub Actions CI (.github/workflows/ci.yml):

   • Reemplazar instalación/ejecución con npm (npm ci, etc.) por Yarn.
   • Usar corepack enable y yarn install --frozen-lockfile.
   • Alinear versión de Node a la usada por Netlify (actualmente 22.21.1 en netlify.toml).
   • Ajustar cache para Yarn.
   • Asegurar que se ejecuten yarn check (astro check) y yarn test (vitest run).

2. Workflow Validate Checkout (.github/workflows/validate-checkout.yml):

   • Alinear Node version a 22.x (idealmente 22.21.1).
   • Mantener Yarn y --frozen-lockfile.

3. Dockerfile:

   • Cambiar instalación a Yarn (via corepack) y usar lockfile (yarn.lock).
   • Evitar npm install.
   • Mantener multi-stage build; runtime debe ejecutar el server de Astro (node ./dist/server/entry.mjs).

4. Verificar que exista yarn.lock y que los workflows usen lo correcto.

   • Si no existe yarn.lock, generarlo de forma coherente (no modificar dependencias salvo que sea necesario).

5. (Opcional pero recomendable) Actualizar README o docs mínimas si mencionan npm para que indiquen Yarn.

Criterios de aceptación:

• Los workflows ya no usan npm.
• Node version queda consistente (preferentemente 22.21.1 o 22.x) en Netlify + GitHub Actions + validate-checkout.
• Build local con Yarn sigue funcionando (yarn install, yarn build).
• Docker build funciona usando Yarn.

Notas:

• No hacer cambios funcionales de negocio; solo tooling/infra.
• Mantener el estilo actual del repo.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: Give me a high level overview of this repo

Assistant: Toallaalacarta is a public Astro 5 + TypeScript e-commerce storefront (based on the Storeplate template) customized for a towels/textiles shop, integrating Shopify Storefront API for catalog data, Appwrite for authentication/data, and payments via Transbank (Webpay Plus) and PayPal. It’s deployed at https://toallaalacarta.netlify.app/ and licensed under MIT.

What it does (at a glance)

• Shopify-powered product catalog (dynamic products via Storefront API / GraphQL)
• Checkout & payments: Transbank (Webpay Plus) + PayPal (capture/authorize)
• User auth: Appwrite
• Admin panel: order + inventory management
• Transactional emails: Resend
• UX features: real-time cart edits, search/sort/filter, tags/categories/variants, image zoom/slider, responsive UI, dynamic home hero slider
• Testing + CI: Vitest + GitHub Actions (lint/tests + checkout validation)

Tech stack & repo shape

• Primary language: TypeScript (~76%), plus Astro components (~17%)
• Framework: Astro (with some React components mentioned in the structure)
• Tooling: Prettier, Vitest, Dockerfile present, Netlify config (netlify.toml)
• Topic tags: ecommerce, typescript, nextjs (tag), towels, chile, business

High-level architecture (from the repo docs)

The repo is organized in a domain/modular style under src/, roughly:

• src/infrastructure/ – external clients/config (e.g., Appwrite singleton)
• src/modules/orders/ – domain business logic (orders)
• src/lib/ – shared utilities (payments/email/cart/content) + shopify/ GraphQL client/queries
• src/layouts/ – Astro + React UI components (storefront/admin/cart)
• src/pages/api/ – HTTP/API layer delegating into services/libs
• src/pages/ – Astro routes/pages
• src/styles/, src/types/ – styling and TS types

Ops / “agent + skills” concept

The repo includes an “operational agent” concept (toallaalacarta-ops) with documented runbooks, secrets mapping, and reusable “Super-Skills” under docs/technical/ (plus a script scripts/validate_checkout.js and a workflow .github/workflows/validate-checkout.yml referenced in the README).

Key entry points if you’re new

• README.md (project overview + setup steps)
• docs/technical/README.md (technical index)
• src/ (implementation)
• .env.example (required environment variables for Shopify/Appwrite/Resend/payments)

If you tell me whether you want a product-level overview (features/user flows) or a developer-level overview (packages, env vars, request flow, where to add features), I can tailor the next summary.

User: ves alguna mejora critica posible de realizar

Assistant: Sí: hay una mejora crítica y bastante “obligatoria” a nivel de confiabilidad del repo: están inconsistentes los gestores de paquetes y versiones de Node entre local/CI/Netlify/Docker. Eso suele romper builds “al azar”, bloquear contribuciones y volver el CI poco confiable.

Mejora crítica #1 (recomendada): unificar Node + package manager en todos los entornos

Ahora mismo:

• package.json declara **`packageMa...

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