Add effective date support for tax rules

Problem Statement:

• When adding a new tax rule in Hospitable, there's no option to set an effective date
• New taxes apply immediately to all future bookings, even if the tax should only start on a specific future date
• This can result in incorrect tax charges on bookings made before the intended effective date

Current Workaround:

• Waiting until the effective date to manually add the tax rule
• This requires careful timing and planning to avoid premature application

Impact:

• Risk of charging incorrect taxes on bookings made before the effective date
• Manual tracking required to know when to add tax rules
• Potential revenue loss or guest billing issues

Proposed Solution:

• Add an "effective date" field when creating or editing tax rules
• Taxes would only apply to bookings created on or after the specified date

Unlock:

• Ability to schedule tax changes for future dates
• Automatic application of new taxes without manual timing
• Accurate tax compliance without risk of premature charges