Cleanup shebangs

[axelstudios]

Any background context you want to provide?

Shebangs (#!) should only be on executable python files that are meant to be run directly, and we only have two such files (manage.py and celery.py)

What's this PR do?

• Removes unnecessary shebangs, and adds a Ruff rule to enforce this
• Removes python 2 basestring usage
• Removes the deprecated, unused check_compressed.py script
• Adds missing copyrights
• Fixes incorrect shebangs
• Fixes bug with guillemet Unicode normalization
• Fixes 4 broken copyright URLs

How should this be manually tested?

Tests should pass