Create a BaseHBVModel class with reusable subroutines (precipitation, snow, soil, response, routing

[MAfarrag]

• Create a BaseHBVModel class with reusable subroutines (precipitation, snow, soil, response, routing).
• Refactor all HBV variants to inherit from BaseHBVModel.
• Standardize inputs (e.g., use dictionaries or dataclasses instead of positional vectors).
• Introduce a configuration structure using pydantic.BaseModel.