Add comprehensive type hints to SCORE2 module

[fbraza]

Issue Description

The SCORE2 implementation is missing type hints for some variables and could benefit from more comprehensive typing.

Current State

• Function signatures have type hints
• Some internal variables lack type hints
• Could improve code clarity and IDE support

Suggested Improvements

1. Add type hints for transformed variables

# Current
cage = (age - 60) / 5
smoking = float(biomarkers.smoking)

# Improved
cage: float = (age - 60) / 5
smoking: float = float(biomarkers.smoking)
csbp: float = (biomarkers.systolic_blood_pressure - 120) / 20
ctchol: float = biomarkers.total_cholesterol - 6
chdl: float = (biomarkers.hdl_cholesterol - 1.3) / 0.5

2. Add type hints for interaction terms

smoking_age: float = smoking * cage
sbp_age: float = csbp * cage
tchol_age: float = ctchol * cage
hdl_age: float = chdl * cage

3. Add type hints for intermediate calculations

x: float = (...)  # Linear predictor
uncalibrated_risk: float = 1 - np.power(baseline_survival, np.exp(x))

4. Consider using TypeAlias for risk categories

from typing import Literal, TypeAlias

RiskCategory: TypeAlias = Literal["Low to moderate", "High", "Very high"]

Impact

• Better IDE support and code completion
• Easier to understand variable types at a glance
• Helps catch type-related bugs early
• Improves code maintainability

Related

• PR feat: Implement SCORE2 cardiovascular risk assessment algorithm #2: feat: Implement SCORE2 cardiovascular risk assessment algorithm
• Follows Python coding style guidelines for clarity

[fbraza]

Fix in #14