Add setting to change standard drink calculation between US/UK

[lucapgiannotti]

Checklist

• I have checked that this feature is not already requested
• I have checked that this feature does not already exist in the project

Is your feature request related to a problem? Please describe.
N/A

Describe the solution you'd like
An option (toggle) in settings where you can change the math for standard drink calculations between U.S. and UK

Additional context
A US “standard drink” contains about 14 g of pure alcohol, while a UK “unit” contains 8 g — meaning 1 US drink ≈ 1.75 UK units