Move create_secrets_files env reads into main

[adamtheturtle]

This refactors admin/create_secrets_files.py so helper functions no longer read from os.environ directly. main() now reads the inactive database environment variables once and passes them through as inactive_database_details. _generate_secrets_file_content() was updated to accept that data and use it when writing the inactive key values. No behavior changes are intended beyond centralizing environment access in main().

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Note

Low Risk
Low risk refactor limited to a dev/admin script; behavior should be unchanged aside from when missing inactive env vars are detected (now read once in main()).

Overview
Refactors admin/create_secrets_files.py so inactive Vuforia credentials are read once in main() (after load_dotenv) and passed into _generate_secrets_file_content() as inactive_database_details, instead of the helper reading os.environ directly.

The generated secrets files now populate the INACTIVE_* entries from that passed-in dict, improving separation of concerns and centralizing environment access.

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