Limit the state's ability to bank statewide mills

This bill prevents certain state-mandated property tax levies from being carried forward to future years if local governments do not use their full authorized tax authority in the current year. It directly affects Montana counties, school districts, and other governmental entities that impose property taxes, specifically limiting how they can bank unused tax mill authority for later use. The key provision amends existing property tax law to exclude specific state-mandated levies - such as those for school districts, regional resource authorities, and certain special assessments - from the ability to carry forward unused tax authority. Local governments will still be able to carry forward unused tax authority for their own discretionary levies, but they cannot do so for taxes required by state law for specific purposes.