Disembark Fix

Bug Fixes

Aircraft could get permanently stuck after landing at multi-leg job destinations (FSC-3929)

When a multi-leg charter job was being configured in the dispatch planner, the system could create a job leg for an onward segment (e.g. KMCO to KSFB) and then clean it up if no passengers ended up needing that leg. The cleanup removed the leg itself but left the previous leg still pointing to it. When the pilot later landed and the system tried to process the arrival, it followed that broken reference and crashed. Every automatic retry hit the same error.

The orphan cleanup now properly maintains the leg chain when removing empty legs, matching the behaviour that already existed in the manual leg deletion path. A migration repairs the one affected job in production.