feat(backend): sprint 2 — simulations + MITRE ATT&CK

- Simulation model with full field set (redteam + SOC sides) and cascade delete
- Alembic migration 0002 for simulations table
- simulation_workflow service: PATCH RBAC field-level + auto-transition pending→in_progress + state machine
- mitre service: STIX bundle loader (boot-safe) + ranked search (exact-id > prefix-id > name)
- 7 new API endpoints: list/create/get/patch/delete simulations, transition, MITRE autocomplete
- serialize_simulation added to serializers.py
- Makefile update-mitre target with real curl + optional docker restart
- Dockerfile updated to copy backend/data/ into image
- MITRE enterprise-attack.json bundle committed (~45 MB)
- 67 new tests (total 130 passing), ruff clean, mypy introduces no new errors

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/api/__init__.py

@@ -1,6 +1,7 @@
 """API blueprints."""
 from backend.app.api.auth import auth_bp
 from backend.app.api.engagements import engagements_bp
+from backend.app.api.simulations import simulations_bp
 from backend.app.api.users import users_bp
 
-__all__ = ["auth_bp", "users_bp", "engagements_bp"]
+__all__ = ["auth_bp", "users_bp", "engagements_bp", "simulations_bp"]