local dev setup + OPENAI_BASE_URL support + dashboard fix

- CLAUDE.md con arquitectura y comandos del proyecto
- env.example: agregar LIMIT_CONVERSATIONS, MAX_CHARS_PER_MESSAGE, OPENAI_BASE_URL
- docker-compose.override: puerto 3001, extra_hosts para modelo local en Linux
- OpenAI clients: soporte OPENAI_BASE_URL para apuntar a modelo local compatible
- stats.js: sync de órdenes en background, dashboard no bloquea al cargar
- package-lock: dbmate movido a prod dependencies

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

env.example

@@ -42,6 +42,12 @@ EVOLUTION_API_KEY=your-api-key
 EVOLUTION_INSTANCE_NAME=piaf
 EVOLUTION_SEND_ENABLED=0   # 0=solo BD (pruebas), 1=envía a WhatsApp (producción)
 
+# ===================
+# Limits
+# ===================
+LIMIT_CONVERSATIONS=100
+MAX_CHARS_PER_MESSAGE=4000
+
 # ===================
 # Debug Flags (1/true/yes/on para activar)
 # ===================