Update the year of the copyright notices

[moritzsommer]

Current Situation

As of now, #450 tried to resolve the issue with the deprecated year in the copyright notices. After the CI passed and the PR got merged, 2 problems remain:

1. The year wasn't changed everywhere, e.g.

   basyx-python-sdk/compliance_tool/aas_compliance_tool/compliance_check_aasx.py

   Line 1 in f831016

   # Copyright (c) 2025 the Eclipse BaSyx Authors

2. Despite this, the CI still passed in Update year of copyright notices in module docstrings #450. But now, it fails due to the old dates.

Proposed Change

We have to search for all occurrences of the year and replace it throughout the whole repository. Moreover, we should find out why the CI is behaving in this manner, because #400 is also linked to the CI randomly failing and passing.

[moritzsommer]

I had a wrong understanding about how the copyright notice date should work. In our scheme, we only change the date of files that we have actively modified. In this case, the file compliance_check_aasx.py was modified, so the CI worked correctly. I was a bit hasty in writing up this issue because we have already had problems with the CI (see #400). Moreover, I propose changing the date format to date of original file - date of last change.