chore(docs): completar Fase 2 — requisitos y arquitectura

- Añade/actualiza `docs/requirements.md`, `docs/architecture.md`, `docs/api-integration.md`, `docs/data-model.md`
- Documenta criterios de aceptación y decisiones técnico-arquitectónicas
- Recomendación: añadir `docs/legal-considerations.md` (pendiente)

backend/src/app.ts

@@ -0,0 +1,24 @@
+import Fastify, { FastifyInstance } from 'fastify';
+import cors from '@fastify/cors';
+import helmet from '@fastify/helmet';
+import rateLimit from '@fastify/rate-limit';
+import healthRoutes from './routes/health';
+
+export function buildApp(): FastifyInstance {
+  const app: FastifyInstance = Fastify({
+    logger: false,
+  });
+
+  void app.register(cors, { origin: true });
+  void app.register(helmet);
+  void app.register(rateLimit, { max: 1000, timeWindow: '1 minute' });
+  void app.register(healthRoutes, { prefix: '/api' });
+
+  return app;
+}
+
+/**
+ * Metadatos:
+ * Autor: GitHub Copilot
+ * Última actualización: 2026-02-07
+ */

backend/src/index.ts

@@ -0,0 +1,29 @@
+import dotenv from 'dotenv';
+import { buildApp } from './app';
+
+dotenv.config();
+
+const port = Number(process.env.PORT ?? 3000);
+const app = buildApp();
+
+const start = async () => {
+  try {
+    await app.listen({ port, host: '0.0.0.0' });
+    // eslint-disable-next-line no-console
+    console.log(`Server listening on http://0.0.0.0:${port}`);
+  } catch (err) {
+    app.log.error(err);
+    process.exit(1);
+  }
+};
+
+// Start only when run directly (avoids starting during tests)
+if (require.main === module) {
+  start();
+}
+
+/**
+ * Metadatos:
+ * Autor: GitHub Copilot
+ * Última actualización: 2026-02-07
+ */

backend/src/plugins/prisma.ts

@@ -0,0 +1,11 @@
+import { PrismaClient } from '@prisma/client';
+
+const prisma = new PrismaClient();
+
+export default prisma;
+
+/**
+ * Metadatos:
+ * Autor: GitHub Copilot
+ * Última actualización: 2026-02-07
+ */

backend/src/routes/health.ts

@@ -0,0 +1,11 @@
+import { FastifyInstance } from 'fastify';
+
+export default async function healthRoutes(app: FastifyInstance) {
+  app.get('/health', async () => ({ status: 'ok' }));
+}
+
+/**
+ * Metadatos:
+ * Autor: GitHub Copilot
+ * Última actualización: 2026-02-07
+ */