Summary of significant accounting policies - Shipping and Handling Costs (Details) - USD ($) |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Accounting Policies [Abstract] | ||||
| Shipping and handling expense | $ 382,603 | $ 342,981 | $ 758,276 | $ 699,135 |