Move subscriptions safely between tiers

A tiered subscription can now be moved directly to another tier from its actions menu. Alunta only offers tiers that satisfy the subscription’s latest reported usage and also verifies that the selected tier has a price for the subscription’s currency and renewal interval.

An upgrade can take effect immediately or at the next period depending on the plan configuration. A downgrade takes effect at the first future period that has not yet been invoiced. The subscription remains active, and automatic upgrades continue after a manual change.

Scheduled tier changes can be inspected and managed through the API. If a later usage or pricing configuration change invalidates a manual change, it is now shown as an integration error instead of disappearing silently.