Previously, the `DATA_DIR` environment variable was always overridden by defaulting to `OPEN_WEBUI_DIR / "data"`, which ignored user-defined `DATA_DIR` values. Additionally, when `DATA_DIR` and `NEW_DATA_DIR` were the same, the script attempted to copy files into themselves, leading to errors or redundant operations.
This commit ensures that:
1. The `DATA_DIR` environment variable is respected and not overridden.
2. Copy operations between `DATA_DIR` and `NEW_DATA_DIR` are only performed if the directories are different, preventing errors when they point to the same location.
These changes resolve potential file copy errors and preserve user configurations.
