Auto-lock tasks created from specific lists

When dragging and dropping from certain lists to create tasks, automatically set them as locked/immutable - similar to how calendar-synced events are auto-locked. This would be helpful for managing collections of fixed commitments (like work meetings) that are frequently created from the same list.

While TimeFinder already auto-locks calendar imports and supports individual task locking, extending auto-lock behavior to list-sourced tasks would streamline the workflow for managing fixed time blocks.