chore(sat): prepara entorno para proxies

- Agrega dependencia https-proxy-agent.
- Documenta variables SAT_PROXY_LIST, SAT_PROXY_STRATEGY y SAT_PROXY_FALLBACK_DIRECT en .env.example.
- Actualiza pnpm-lock.yaml.

apps/api/package.json

@@ -35,6 +35,7 @@
     "facturapi": "^4.14.2",
     "fast-xml-parser": "^5.3.3",
     "helmet": "^8.0.0",
+    "https-proxy-agent": "^7.0.6",
     "jsonwebtoken": "^9.0.2",
     "mercadopago": "^2.12.0",
     "node-cron": "^4.2.1",