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/config_bp.py

@@ -13,15 +13,53 @@ config_bp = Blueprint('config', __name__, url_prefix='/pos/api/config')
 def list_branches():
     conn = get_tenant_conn(g.tenant_id)
     cur = conn.cursor()
-    cur.execute("SELECT id, name, address, phone, is_active FROM branches ORDER BY id")
+    cur.execute("""
+        SELECT id, name, address, phone, is_active, is_main,
+               rfc, razon_social, regimen_fiscal, codigo_postal,
+               serie_cfdi, folio_inicial, licencia_fiscal
+        FROM branches ORDER BY id
+    """)
     branches = []
     for r in cur.fetchall():
-        branches.append({'id': r[0], 'name': r[1], 'address': r[2], 'phone': r[3], 'is_active': r[4]})
+        branches.append({
+            'id': r[0], 'name': r[1], 'address': r[2], 'phone': r[3],
+            'is_active': r[4], 'is_main': r[5],
+            'rfc': r[6], 'razon_social': r[7], 'regimen_fiscal': r[8],
+            'codigo_postal': r[9], 'serie_cfdi': r[10],
+            'folio_inicial': r[11], 'licencia_fiscal': r[12],
+        })
     cur.close()
     conn.close()
     return jsonify({'data': branches})
 
 
+@config_bp.route('/branches/<int:branch_id>', methods=['GET'])
+@require_auth('config.view')
+def get_branch(branch_id):
+    conn = get_tenant_conn(g.tenant_id)
+    cur = conn.cursor()
+    cur.execute("""
+        SELECT id, name, address, phone, is_active, is_main,
+               rfc, razon_social, regimen_fiscal, codigo_postal,
+               serie_cfdi, folio_inicial, licencia_fiscal,
+               certificado_pem, llave_pem
+        FROM branches WHERE id = %s
+    """, (branch_id,))
+    r = cur.fetchone()
+    cur.close()
+    conn.close()
+    if not r:
+        return jsonify({'error': 'Branch not found'}), 404
+    return jsonify({
+        'id': r[0], 'name': r[1], 'address': r[2], 'phone': r[3],
+        'is_active': r[4], 'is_main': r[5],
+        'rfc': r[6], 'razon_social': r[7], 'regimen_fiscal': r[8],
+        'codigo_postal': r[9], 'serie_cfdi': r[10],
+        'folio_inicial': r[11], 'licencia_fiscal': r[12],
+        'certificado_pem': r[13], 'llave_pem': r[14],
+    })
+
+
 @config_bp.route('/branches', methods=['POST'])
 @require_auth('config.edit')
 def create_branch():
@@ -47,10 +85,25 @@ def create_branch():
 
     conn = get_tenant_conn(g.tenant_id)
     cur = conn.cursor()
+
+    # If setting as main, clear any existing main
+    if data.get('is_main'):
+        cur.execute("UPDATE branches SET is_main = false WHERE is_main = true")
+
     cur.execute("""
-        INSERT INTO branches (name, address, phone)
-        VALUES (%s, %s, %s) RETURNING id
-    """, (data['name'], data.get('address'), data.get('phone')))
+        INSERT INTO branches (
+            name, address, phone, is_main,
+            rfc, razon_social, regimen_fiscal, codigo_postal,
+            serie_cfdi, folio_inicial, licencia_fiscal,
+            certificado_pem, llave_pem
+        )
+        VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s) RETURNING id
+    """, (
+        data['name'], data.get('address'), data.get('phone'), bool(data.get('is_main')),
+        data.get('rfc'), data.get('razon_social'), data.get('regimen_fiscal'), data.get('codigo_postal'),
+        data.get('serie_cfdi'), data.get('folio_inicial'), data.get('licencia_fiscal'),
+        data.get('certificado_pem'), data.get('llave_pem'),
+    ))
     branch_id = cur.fetchone()[0]
     conn.commit()
     cur.close()
@@ -58,6 +111,50 @@ def create_branch():
     return jsonify({'id': branch_id, 'message': 'Branch created'}), 201
 
 
+@config_bp.route('/branches/<int:branch_id>', methods=['PUT'])
+@require_auth('config.edit')
+def update_branch(branch_id):
+    data = request.get_json() or {}
+    conn = get_tenant_conn(g.tenant_id)
+    cur = conn.cursor()
+
+    cur.execute("SELECT id FROM branches WHERE id = %s", (branch_id,))
+    if not cur.fetchone():
+        cur.close(); conn.close()
+        return jsonify({'error': 'Branch not found'}), 404
+
+    # If setting as main, clear any existing main
+    if data.get('is_main'):
+        cur.execute("UPDATE branches SET is_main = false WHERE is_main = true AND id <> %s", (branch_id,))
+
+    updates = []
+    params = []
+    field_map = {
+        'name': 'name', 'address': 'address', 'phone': 'phone',
+        'is_active': 'is_active', 'is_main': 'is_main',
+        'rfc': 'rfc', 'razon_social': 'razon_social',
+        'regimen_fiscal': 'regimen_fiscal', 'codigo_postal': 'codigo_postal',
+        'serie_cfdi': 'serie_cfdi', 'folio_inicial': 'folio_inicial',
+        'licencia_fiscal': 'licencia_fiscal',
+        'certificado_pem': 'certificado_pem', 'llave_pem': 'llave_pem',
+    }
+    for json_key, col in field_map.items():
+        if json_key in data:
+            updates.append(f"{col} = %s")
+            params.append(data[json_key])
+
+    if not updates:
+        cur.close(); conn.close()
+        return jsonify({'error': 'Nothing to update'}), 400
+
+    params.append(branch_id)
+    cur.execute(f"UPDATE branches SET {', '.join(updates)} WHERE id = %s", params)
+    conn.commit()
+    cur.close()
+    conn.close()
+    return jsonify({'ok': True, 'message': 'Branch updated'})
+
+
 @config_bp.route('/employees', methods=['GET'])
 @require_auth('config.view')
 def list_employees():