Fix the use of wildcard import sign (*) in all __init__.py files

[mraffly]

Purpose of the improvement

This refers to point 5.1 in the documentation https://iffmd.fz-juelich.de/zXxTrardSNaJc4a22gNypw?view

When it comes to importing, wildcard import sign is used in all init.py, such as this line in

FINE/fine/__init__.py

Line 15 in c28d5b8

from .subclasses import *

Example from fine/init.py

from .subclasses import *
from .IOManagement import *
from .aggregations import *

This can cause the following issues:

• Makes it unclear which symbols are exported
• Can lead to namespace pollution
• Harder to track where imports come from
• Ruff linter specifically ignores F403 (wildcard import warnings) in config

Proposal

Hence, fixing this is desirable (if necessary) and could be done by doing so:

• Define explicit all lists in each module
• Or migrate to explicit imports in init.py files
• Note: This is a large refactor affecting the entire project structure

NOTES:

Do we want to prevent wildcard imports?