feat(config): agrega personalización de ticket con logo y opciones

- Nuevos endpoints /pos/api/config/receipt (GET/PUT)
- Sección en config.html para subir logo, datos del negocio y toggles visuales
- pos.js carga la config y renderiza el ticket usando logo, RFC, dirección,
  teléfono, mensajes y opciones de desglose/empleado/pago configurables
- Logo se redimensiona a 300px de ancho y se guarda como base64 JPEG en tenant_config

Tests: 35 passed

pos/blueprints/config_bp.py

@@ -752,3 +752,99 @@ def set_onboarding_status():
     cur.close()
     conn.close()
     return jsonify({'completed': completed == 'true'})
+
+
+# ─── Receipt / Ticket Customization ────────────────────────────────────────
+
+RECEIPT_CONFIG_KEYS = [
+    'receipt_logo',
+    'receipt_store_name',
+    'receipt_tagline',
+    'receipt_rfc',
+    'receipt_address',
+    'receipt_phone',
+    'receipt_footer',
+    'receipt_thanks_message',
+    'receipt_show_logo',
+    'receipt_show_rfc',
+    'receipt_show_address',
+    'receipt_show_phone',
+    'receipt_show_iva_breakdown',
+    'receipt_show_payment_details',
+    'receipt_show_employee',
+]
+
+
+@config_bp.route('/receipt', methods=['GET'])
+@require_auth('pos.view')
+def get_receipt_config():
+    """Get receipt customization settings."""
+    conn = get_tenant_conn(g.tenant_id)
+    cur = conn.cursor()
+    cur.execute(
+        "SELECT key, value FROM tenant_config WHERE key = ANY(%s)",
+        (RECEIPT_CONFIG_KEYS,)
+    )
+    rows = {row[0]: row[1] for row in cur.fetchall()}
+    cur.close()
+    conn.close()
+
+    def _bool(key, default=False):
+        v = rows.get(key, 'true' if default else 'false')
+        return str(v).lower() == 'true'
+
+    return jsonify({
+        'logo': rows.get('receipt_logo', ''),
+        'store_name': rows.get('receipt_store_name', ''),
+        'tagline': rows.get('receipt_tagline', ''),
+        'rfc': rows.get('receipt_rfc', ''),
+        'address': rows.get('receipt_address', ''),
+        'phone': rows.get('receipt_phone', ''),
+        'footer': rows.get('receipt_footer', ''),
+        'thanks_message': rows.get('receipt_thanks_message', 'Gracias por su compra!'),
+        'show_logo': _bool('receipt_show_logo', True),
+        'show_rfc': _bool('receipt_show_rfc', True),
+        'show_address': _bool('receipt_show_address', False),
+        'show_phone': _bool('receipt_show_phone', False),
+        'show_iva_breakdown': _bool('receipt_show_iva_breakdown', True),
+        'show_payment_details': _bool('receipt_show_payment_details', True),
+        'show_employee': _bool('receipt_show_employee', False),
+    })
+
+
+@config_bp.route('/receipt', methods=['PUT'])
+@require_auth('config.edit')
+def update_receipt_config():
+    """Update receipt customization settings."""
+    data = request.get_json() or {}
+    conn = get_tenant_conn(g.tenant_id)
+    cur = conn.cursor()
+
+    settings = {
+        'receipt_logo': data.get('logo', ''),
+        'receipt_store_name': data.get('store_name', ''),
+        'receipt_tagline': data.get('tagline', ''),
+        'receipt_rfc': data.get('rfc', ''),
+        'receipt_address': data.get('address', ''),
+        'receipt_phone': data.get('phone', ''),
+        'receipt_footer': data.get('footer', ''),
+        'receipt_thanks_message': data.get('thanks_message', 'Gracias por su compra!'),
+        'receipt_show_logo': 'true' if data.get('show_logo') else 'false',
+        'receipt_show_rfc': 'true' if data.get('show_rfc') else 'false',
+        'receipt_show_address': 'true' if data.get('show_address') else 'false',
+        'receipt_show_phone': 'true' if data.get('show_phone') else 'false',
+        'receipt_show_iva_breakdown': 'true' if data.get('show_iva_breakdown') else 'false',
+        'receipt_show_payment_details': 'true' if data.get('show_payment_details') else 'false',
+        'receipt_show_employee': 'true' if data.get('show_employee') else 'false',
+    }
+
+    for key, value in settings.items():
+        cur.execute("""
+            INSERT INTO tenant_config (key, value) VALUES (%s, %s)
+            ON CONFLICT (key) DO UPDATE SET value = EXCLUDED.value
+        """, (key, value))
+
+    conn.commit()
+    cur.close()
+    conn.close()
+    return jsonify({'message': 'Receipt configuration updated'})