FASE 4-5-6: Infraestructura, CRM, Service Orders, Notificaciones, Ahorro, Logistica, API Publica

FASE 4:
- Redis cache de stock con fallback graceful
- Multi-moneda (MXN/USD) con contabilidad en MXN
- Proveedores y ordenes de compra completo
- Meilisearch 1.5M+ partes indexadas
- Metabase KPIs con dashboard auto-generado

FASE 5:
- CRM mejorado: activities, tags, loyalty program, analytics
- Imagenes de partes: upload, resize, thumbnails WebP
- Ordenes de servicio Kanban: received->diagnosis->repair->ready->delivered
- Garantias/RMA, alertas de reorden, multi-sucursal
- Stubs BNPL (APLAZO) y ERP Sync (Aspel/Contpaqi)

FASE 6:
- Notificaciones automaticas: push/WhatsApp/email/in-app
- Reportes de ahorro vs retail_price
- Logistica + tracking: DHL, FedEx, Estafeta, 99min, Uber
- API Publica: API keys, rate limiting, catalog search

Migraciones: v1.9-v3.0
Tests: 93/93 pasando
Backup: nexus_backup_20260427_045859.tar.gz

pos/migrations/v1.9_redis_cache.sql

@@ -0,0 +1,18 @@
+-- v1.9_redis_cache.sql
+-- Mejora #9: Caché de Stock con Redis
+--
+-- Adds Redis-backed stock caching for sub-millisecond lookups.
+-- No database schema changes required — caching is handled entirely
+-- in the application layer (pos/services/redis_stock_cache.py).
+--
+-- Invalidation strategy:
+--   - Every stock mutation (SALE, PURCHASE, RETURN, ADJUST, TRANSFER, INITIAL)
+--     invalidates the affected Redis keys immediately in Python code.
+--   - Cache TTL is 5 minutes (configurable via REDIS_STOCK_TTL env var).
+--   - On Redis miss, stock is computed from PostgreSQL SUM query and cached.
+--
+-- Prerequisites:
+--   - Redis server installed and running (default: localhost:6379)
+--   - redis-py library installed
+--
+SELECT 'v1.9 redis cache migration applied' as status;