Creates versioned Alembic migration scripts with tables, columns, primary keys, foreign keys, unique and functional constraints (e.g. case-insensitive uniqueness), and reference-data seeds, all derived from the entity model. Use when the user asks to "create a migration", "add a database migration", "write an Alembic migration", "add a column", "add a foreign key", "seed reference data", or mentions Alembic, schema migration, or database schema changes.