Agent Skills: django-models

Design Django ORM models for Sentry following architectural conventions for silos, replication, relocation, and foreign keys. Use when adding a new Django model, designing a model for a feature, deciding where data should live, picking a foreign key type, or refactoring an existing model's silo placement. Trigger on "add a Django model", "create a model", "design a model for X", "new database table", "store this data in the DB", "I need to track Y", "model for [feature]". Not for Pydantic models, dataclasses, ML models, or Protobuf — this is specifically for Django ORM models in the Sentry codebase.