Credential disclosure via Git credential store

Credential exposure in Git handling in ha-china Blueprint Studio before 2.5.2 allows local users to read access tokens via local files. In custom_components/blueprint_studio/backend/git_manager.py, the set_credentials workflow configures Git's credential.helper store, which writes the supplied username and token in plaintext to the Home Assistant user's .git-credentials file and leaves that helper active for later Git commands. Admin-level access to save Git credentials is required to trigger the write, and later exposure is limited to other users or processes that can read the same filesystem context.