feat(F-001): scaffold modular monolith skeleton with boundary checker

- TypeScript + Fastify skeleton under project/ (src/modules, shared, infrastructure, app)
- scripts/check-module-boundaries.mjs enforcing module public-API rules (tested with fixtures)
- GET /health endpoint, error envelope without stack leakage
- specs/F-001-scaffold (SPEC/DESIGN/TASKS/TESTS), spec/tech.md dependency justification
- 30-ticket MercadoDeVida roadmap in backlog/features.json, spec/roadmap.md
- All gates approved: reviewer, security, qa; verify.sh green

spec/product.md

@@ -0,0 +1,15 @@
+# Product Spec
+
+## Problema
+Describe el problema de negocio.
+
+## Objetivo
+Define el resultado esperado del producto.
+
+## Usuarios
+- Usuario principal:
+- Usuario secundario:
+
+## Alcance v1
+- In scope:
+- Out of scope: