5.0.0

• Restore django-fsm as an independently maintained package with Viewflow FSM engine under the hood.
• Make Django dependency optional: the pure-Python State API, chart(), can_proceed(), and has_transition_perm() work without Django installed.
• Django model adapters (FSMField, FSMIntegerField, FSMKeyField) and @transition(field=...) are available with Django installed or via pip install 'django-fsm[django]'.
• Add State, forward references (this), dynamic targets (RETURN_VALUE, GET_STATE), and optional Viewflow Pro / DRF modules.
• Preserve backward-compatible APIs for model-backed fields, conditions, permissions, signals, error targets, and optimistic locking (ConcurrentTransitionMixin).
• Require Python 3.10+; Django 5.2+ / 6.0+ supported.
• Use AGPL-3.0-or-later with the Viewflow Library Exception, retaining the original MIT notice in LICENSE_LEGACY.