Income taxes - Net long-term deferred tax liability (Details) - USD ($)	Dec. 31, 2025	Dec. 31, 2024
Deferred tax assets:
Net operating loss carryforwards	$ 212,772	$ 80,285
Accruals and reserves	220,343	209,549
Operating lease liabilities	439,254	425,797
Capitalized research expenditures	0	316,937
Others	156,196	88,750
Valuation allowances	0	0
Deferred tax assets	1,028,565	1,121,318
Deferred tax liabilities:
Property and equipment	764,116	239,830
Intangible assets	525,359	672,973
Operating lease right-of-use assets	433,058	419,408
Others	13,476	0
Deferred Tax Liabilities, Gross	1,736,009	1,332,211
Net deferred tax liability	$ 707,444	$ 210,893