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/blueprints/savings_bp.py

@@ -0,0 +1,108 @@
+"""Savings Blueprint: retail price management and savings reports.
+
+Prefix: /pos/api/savings
+"""
+
+from flask import Blueprint, request, jsonify, g
+from middleware import require_auth
+from tenant_db import get_tenant_conn
+from services.savings_engine import (
+    get_customer_savings_report, get_global_savings_stats, calculate_item_savings,
+)
+
+savings_bp = Blueprint('savings', __name__, url_prefix='/pos/api/savings')
+
+
+@savings_bp.route('/inventory/<int:item_id>/retail-price', methods=['PUT'])
+@require_auth()
+def set_retail_price(item_id):
+    data = request.get_json() or {}
+    retail_price = data.get('retail_price')
+    if retail_price is None:
+        return jsonify({'error': 'retail_price is required'}), 400
+
+    conn = get_tenant_conn(g.tenant_id)
+    try:
+        cur = conn.cursor()
+        cur.execute("""
+            UPDATE inventory SET retail_price = %s WHERE id = %s
+        """, (retail_price, item_id))
+        conn.commit()
+        cur.close()
+        return jsonify({'message': 'Retail price updated'})
+    finally:
+        conn.close()
+
+
+@savings_bp.route('/inventory/bulk-retail-price', methods=['POST'])
+@require_auth()
+def bulk_set_retail_price():
+    """Bulk update retail prices from CSV/JSON.
+
+    Body: {"items": [{"item_id": 1, "retail_price": 100.00}, ...]}
+    """
+    data = request.get_json() or {}
+    items = data.get('items', [])
+    if not items:
+        return jsonify({'error': 'items array is required'}), 400
+
+    conn = get_tenant_conn(g.tenant_id)
+    try:
+        cur = conn.cursor()
+        updated = 0
+        for item in items:
+            item_id = item.get('item_id')
+            retail_price = item.get('retail_price')
+            if item_id and retail_price is not None:
+                cur.execute("""
+                    UPDATE inventory SET retail_price = %s WHERE id = %s
+                """, (retail_price, item_id))
+                updated += cur.rowcount
+        conn.commit()
+        cur.close()
+        return jsonify({'updated': updated, 'message': f'{updated} prices updated'})
+    finally:
+        conn.close()
+
+
+@savings_bp.route('/customers/<int:customer_id>', methods=['GET'])
+@require_auth()
+def customer_savings(customer_id):
+    months = int(request.args.get('months', 12))
+    conn = get_tenant_conn(g.tenant_id)
+    try:
+        report = get_customer_savings_report(conn, customer_id, months=months)
+        return jsonify(report)
+    finally:
+        conn.close()
+
+
+@savings_bp.route('/stats', methods=['GET'])
+@require_auth()
+def global_savings():
+    from_date = request.args.get('from_date')
+    to_date = request.args.get('to_date')
+    conn = get_tenant_conn(g.tenant_id)
+    try:
+        stats = get_global_savings_stats(conn, g.tenant_id, from_date=from_date, to_date=to_date)
+        return jsonify(stats)
+    finally:
+        conn.close()
+
+
+@savings_bp.route('/calculate', methods=['POST'])
+@require_auth()
+def calculate_savings():
+    """Calculate savings for a given price vs retail."""
+    data = request.get_json() or {}
+    unit_price = float(data.get('unit_price', 0))
+    retail_price = float(data.get('retail_price', 0))
+    quantity = int(data.get('quantity', 1))
+    savings, pct = calculate_item_savings(unit_price, retail_price, quantity)
+    return jsonify({
+        'unit_price': unit_price,
+        'retail_price': retail_price,
+        'quantity': quantity,
+        'savings_amount': savings,
+        'savings_percentage': pct,
+    })