feat: Fase 1-3 completas - precios proveedor, multi-sucursal, factura global

Fase 1: Lista de precios de proveedor
- Tabla supplier_catalog_prices en master DB
- Endpoints GET/POST/PUT/DELETE /supplier-catalog/prices
- Upload CSV/Excel de precios de proveedor
- Visualizacion de supplier_price en catalogo y POS

Fase 2: Multi-sucursal completo
- Migracion v4.0: inventory.branch_id=NULL, tabla inventory_stock
- Campos fiscales en branches (RFC, regimen, CP, serie CFDI, certificados)
- Trigger trg_update_inventory_stock para sincronizar stock por sucursal
- Backend config_bp.py con CRUD de sucursales fiscales
- Backend inventory_bp.py y pos_bp.py refactorizados para inventario compartido
- Backend invoicing_bp.py usa datos fiscales de la sucursal de la venta
- Frontend config.html/js con modal de sucursales expandido

Fase 3: Factura global mensual
- Migracion v4.1: tablas global_invoice_sales, sales.global_invoiced_at
- build_global_invoice_xml() con InformacionGlobal SAT-compliant
- Servicio global_invoice.py para agrupar ventas PUE <=000
- Endpoints POST/GET /global-invoice y /global-invoice/eligible-sales
- Frontend invoicing.html/js con boton y modal de factura global

pos/blueprints/invoicing_bp.py

@@ -6,6 +6,7 @@ This blueprint is the HTTP layer that validates input and returns JSON.
 """
 
 import json
+from datetime import datetime
 from flask import Blueprint, request, jsonify, g
 from middleware import require_auth
 from tenant_db import get_tenant_conn
@@ -19,17 +20,19 @@ from services.audit import log_action
 invoicing_bp = Blueprint('invoicing', __name__, url_prefix='/pos/api/invoicing')
 
 
-def _get_tenant_config(cur):
-    """Load tenant CFDI configuration from tenant_config table.
+def _get_issuer_config(cur, branch_id=None):
+    """Load CFDI issuer configuration.
 
-    Falls back to sensible defaults if config is incomplete.
+    If branch_id is provided and the branch has fiscal data, use it.
+    Otherwise fall back to tenant-level config.
     """
+    # Tenant-level defaults
     config = {}
     cur.execute("SELECT key, value FROM tenant_config WHERE key LIKE 'cfdi_%' OR key LIKE 'tenant_%'")
     for row in cur.fetchall():
         config[row[0]] = row[1]
 
-    return {
+    result = {
         'rfc': config.get('tenant_rfc', ''),
         'razon_social': config.get('tenant_razon_social', ''),
         'regimen_fiscal': config.get('cfdi_regimen_fiscal', '601'),
@@ -39,6 +42,22 @@ def _get_tenant_config(cur):
         'horux_api_key': config.get('cfdi_horux_api_key', ''),
     }
 
+    # Branch-level override
+    if branch_id:
+        cur.execute("""
+            SELECT rfc, razon_social, regimen_fiscal, codigo_postal, serie_cfdi
+            FROM branches WHERE id = %s
+        """, (branch_id,))
+        row = cur.fetchone()
+        if row and row[0]:
+            result['rfc'] = row[0] or result['rfc']
+            result['razon_social'] = row[1] or result['razon_social']
+            result['regimen_fiscal'] = row[2] or result['regimen_fiscal']
+            result['cp'] = row[3] or result['cp']
+            result['serie'] = row[4] or result['serie']
+
+    return result
+
 
 def _get_sale_with_items(cur, sale_id):
     """Load a sale with its items for CFDI generation."""
@@ -134,14 +153,14 @@ def generate_invoice():
     cur = conn.cursor()
 
     try:
-        tenant_config = _get_tenant_config(cur)
-        if not tenant_config['rfc']:
-            return jsonify({'error': 'Tenant RFC not configured. Set tenant_rfc in config.'}), 400
-
         sale = _get_sale_with_items(cur, sale_id)
         if not sale:
             return jsonify({'error': 'Sale not found'}), 404
 
+        tenant_config = _get_issuer_config(cur, sale.get('branch_id'))
+        if not tenant_config['rfc']:
+            return jsonify({'error': 'Tenant RFC not configured. Set tenant_rfc in config.'}), 400
+
         if sale['status'] == 'cancelled':
             return jsonify({'error': 'Cannot invoice a cancelled sale'}), 400
 
@@ -261,7 +280,7 @@ def trigger_process_queue():
     cur = conn.cursor()
 
     try:
-        tenant_config = _get_tenant_config(cur)
+        tenant_config = _get_issuer_config(cur)
         horux_url = tenant_config.get('horux_api_url')
         horux_key = tenant_config.get('horux_api_key')
 
@@ -316,7 +335,7 @@ def cancel_invoice(cfdi_id):
     cur = conn.cursor()
 
     try:
-        tenant_config = _get_tenant_config(cur)
+        tenant_config = _get_issuer_config(cur)
         result = cancel_cfdi(
             conn, cfdi_id, motive, replacement_uuid,
             tenant_config.get('horux_api_url'),
@@ -362,7 +381,7 @@ def get_sale_pdf(sale_id):
         cur.close(); conn.close()
         return jsonify({'error': 'Sale not found'}), 404
 
-    tenant_config = _get_tenant_config(cur)
+    tenant_config = _get_issuer_config(cur, sale.get('branch_id'))
     customer = _get_customer(cur, sale.get('customer_id'))
 
     # Check if there's a stamped CFDI
@@ -424,3 +443,102 @@ def api_invoicing_stats():
         'complementos': row[2] or 0,
         'cancelaciones': row[3] or 0,
     })
+
+
+@invoicing_bp.route('/global-invoice', methods=['POST'])
+@require_auth('invoicing.create')
+def generate_global_invoice():
+    """Generate a monthly global invoice for cash sales.
+
+    Body: {
+        year: int (default current year),
+        month: int (default current month),
+        branch_id: int (optional)
+    }
+    """
+    data = request.get_json() or {}
+    now = datetime.now()
+    year = data.get('year', now.year)
+    month = data.get('month', now.month)
+    branch_id = data.get('branch_id')
+
+    try:
+        year = int(year)
+        month = int(month)
+        if month < 1 or month > 12:
+            return jsonify({'error': 'month must be 1-12'}), 400
+    except (ValueError, TypeError):
+        return jsonify({'error': 'year and month must be integers'}), 400
+
+    conn = get_tenant_conn(g.tenant_id)
+    cur = conn.cursor()
+
+    tenant_config = _get_issuer_config(cur, branch_id)
+    if not tenant_config['rfc']:
+        cur.close(); conn.close()
+        return jsonify({'error': 'Tenant RFC not configured'}), 400
+
+    from services.global_invoice import generate_global_invoice
+    result = generate_global_invoice(
+        conn, tenant_config, year, month,
+        branch_id=branch_id,
+        employee_id=getattr(g, 'employee_id', None)
+    )
+
+    if 'error' in result:
+        cur.close(); conn.close()
+        return jsonify(result), 400
+
+    log_action(conn, 'GLOBAL_INVOICE_CREATE', 'cfdi_queue', result['id'],
+               new_value={'year': year, 'month': month, 'sales_count': result['sales_count']})
+    conn.commit()
+    cur.close()
+    conn.close()
+
+    return jsonify(result), 201
+
+
+@invoicing_bp.route('/global-invoice/<int:cfdi_id>', methods=['GET'])
+@require_auth('invoicing.view')
+def get_global_invoice(cfdi_id):
+    """Get status and linked sales of a global invoice."""
+    conn = get_tenant_conn(g.tenant_id)
+    cur = conn.cursor()
+
+    from services.global_invoice import get_global_invoice_status
+    result = get_global_invoice_status(conn, cfdi_id)
+
+    cur.close()
+    conn.close()
+
+    if not result:
+        return jsonify({'error': 'Global invoice not found'}), 404
+
+    return jsonify(result)
+
+
+@invoicing_bp.route('/global-invoice/eligible-sales', methods=['GET'])
+@require_auth('invoicing.view')
+def get_eligible_sales_for_global():
+    """Preview sales that would be included in a global invoice.
+
+    Query params: year, month, branch_id
+    """
+    now = datetime.now()
+    year = request.args.get('year', now.year, type=int)
+    month = request.args.get('month', now.month, type=int)
+    branch_id = request.args.get('branch_id', type=int)
+
+    conn = get_tenant_conn(g.tenant_id)
+
+    from services.global_invoice import get_eligible_sales
+    sales = get_eligible_sales(conn, year, month, branch_id)
+
+    conn.close()
+
+    return jsonify({
+        'year': year, 'month': month,
+        'count': len(sales),
+        'total': sum(s['total'] for s in sales),
+        'sales': [{'id': s['id'], 'total': s['total'], 'created_at': s['created_at']} for s in sales],
+    })