BUG-001 — Age boundary of 18 is incorrectly rejected

Priority: High
Severity: Major
Environment: Chrome 128, desktop
Steps to reproduce:
1. Open the registration form
2. Fill in all fields with valid data
3. Enter 18 in the "Age" field
4. Click "Create account"
Expected result: Registration succeeds (the hint under the field states "registration is open from 18 years old")
Actual result: The form shows the error "Age must be between 18 and 99"
Notes: Looks like a classic off-by-one error in the comparison condition (<= used instead of <)