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/v2.6_bnpl_erp.sql

@@ -0,0 +1,80 @@
+-- v2.6 BNPL (APLAZO) and ERP Sync stubs
+
+-- BNPL / External credit provider transactions
+CREATE TABLE IF NOT EXISTS bnpl_transactions (
+    id SERIAL PRIMARY KEY,
+    tenant_id INTEGER NOT NULL,
+    customer_id INTEGER REFERENCES customers(id),
+    sale_id INTEGER REFERENCES sales(id),
+    provider VARCHAR(50) NOT NULL DEFAULT 'aplazo', -- 'aplazo', 'kueski', 'clip'
+    provider_transaction_id VARCHAR(200),
+    amount NUMERIC(12,2) NOT NULL,
+    status VARCHAR(30) DEFAULT 'pending', -- pending, approved, rejected, funded, cancelled, refunded
+    installment_count INTEGER DEFAULT 1,
+    installment_amount NUMERIC(12,2),
+    customer_fee NUMERIC(12,2) DEFAULT 0,
+    merchant_fee NUMERIC(12,2) DEFAULT 0,
+    provider_response JSONB,
+    webhook_payload JSONB,
+    created_at TIMESTAMPTZ DEFAULT NOW(),
+    updated_at TIMESTAMPTZ DEFAULT NOW()
+);
+CREATE INDEX IF NOT EXISTS idx_bnpl_sale ON bnpl_transactions(sale_id);
+CREATE INDEX IF NOT EXISTS idx_bnpl_customer ON bnpl_transactions(customer_id);
+CREATE INDEX IF NOT EXISTS idx_bnpl_status ON bnpl_transactions(status);
+
+-- ERP Sync configurations per tenant
+CREATE TABLE IF NOT EXISTS erp_sync_configs (
+    id SERIAL PRIMARY KEY,
+    tenant_id INTEGER NOT NULL,
+    erp_type VARCHAR(50) NOT NULL, -- 'aspel_sae', 'contpaqi', 'sap_b1', 'odoo'
+    is_active BOOLEAN DEFAULT FALSE,
+    api_endpoint VARCHAR(500),
+    api_username VARCHAR(200),
+    api_password_encrypted TEXT,
+    database_name VARCHAR(200),
+    company_code VARCHAR(50),
+    sync_direction VARCHAR(20) DEFAULT 'bidirectional', -- 'to_erp', 'from_erp', 'bidirectional'
+    sync_inventory BOOLEAN DEFAULT FALSE,
+    sync_sales BOOLEAN DEFAULT FALSE,
+    sync_customers BOOLEAN DEFAULT FALSE,
+    sync_frequency_minutes INTEGER DEFAULT 60,
+    last_sync_at TIMESTAMPTZ,
+    last_sync_error TEXT,
+    created_at TIMESTAMPTZ DEFAULT NOW(),
+    updated_at TIMESTAMPTZ DEFAULT NOW()
+);
+CREATE UNIQUE INDEX IF NOT EXISTS idx_erp_config_tenant ON erp_sync_configs(tenant_id, erp_type);
+
+-- ERP Sync logs (each sync run)
+CREATE TABLE IF NOT EXISTS erp_sync_logs (
+    id SERIAL PRIMARY KEY,
+    config_id INTEGER REFERENCES erp_sync_configs(id),
+    sync_type VARCHAR(50) NOT NULL, -- 'inventory', 'sales', 'customers', 'full'
+    direction VARCHAR(20) NOT NULL, -- 'to_erp', 'from_erp'
+    status VARCHAR(20) DEFAULT 'running', -- running, success, partial, failed
+    records_processed INTEGER DEFAULT 0,
+    records_failed INTEGER DEFAULT 0,
+    error_message TEXT,
+    details JSONB,
+    started_at TIMESTAMPTZ DEFAULT NOW(),
+    completed_at TIMESTAMPTZ
+);
+CREATE INDEX IF NOT EXISTS idx_erp_logs_config ON erp_sync_logs(config_id, started_at DESC);
+
+-- ERP Sync queue (pending items to sync)
+CREATE TABLE IF NOT EXISTS erp_sync_queue (
+    id SERIAL PRIMARY KEY,
+    config_id INTEGER NOT NULL REFERENCES erp_sync_configs(id),
+    entity_type VARCHAR(50) NOT NULL, -- 'inventory', 'sale', 'customer'
+    entity_id INTEGER NOT NULL,
+    action VARCHAR(20) NOT NULL, -- 'create', 'update', 'delete'
+    priority INTEGER DEFAULT 5, -- 1=urgent, 10=low
+    status VARCHAR(20) DEFAULT 'pending', -- pending, processing, completed, failed
+    retry_count INTEGER DEFAULT 0,
+    last_error TEXT,
+    created_at TIMESTAMPTZ DEFAULT NOW(),
+    processed_at TIMESTAMPTZ
+);
+CREATE INDEX IF NOT EXISTS idx_erp_queue_pending ON erp_sync_queue(config_id, status, priority, created_at)
+    WHERE status IN ('pending', 'failed');