Add a new script that constructs a Windows BCD store offline from Linux using hivex.
The script copies the BCD-Template from Windows and patches string elements.
However, the binary device element encoding (GPT partition info) is not reliably
encoded in this implementation, so the script returns exit code 1 to trigger
fallback to the WinPE-based fws-windows-bcdfix which uses the official bcdboot tool.
Args: ESP_MOUNT WIN_MOUNT WINDOWS_PARTUUID DISK_GUID
Exit codes: 0 = BCD written safely; 1 = fallback to WinPE approach
