Postgres enum labels uppercase but Python StrEnum values lowercase — raw SQL footgun

[antosubash]

Fixed in #87 — simple_module_db.migrations.render_item now emits sa.Enum(..., values_callable=lambda e: [m.value for m in e]) for StrEnum columns, so Postgres labels match the lowercase StrEnum values rather than uppercase attribute names. See framework/db/simple_module_db/migrations.py:133.