Add type hints to Zero-DCE model functions

[geetanunakani]

Description

Added Python type hints to improve readability and static type checking support for the Zero-DCE model implementation.

Changes

• Added -> None return type to __init__()
• Added -> None return type to _init_weights()
• Added explicit return type Tuple[torch.Tensor, torch.Tensor] to forward()
• Added typed configuration parameter using Optional[Dict[str, Any]] in build_zero_dce()
• Added required typing imports

Fixes #12