Add a backend migration in adepthood

Create and apply an Alembic migration for a schema change in Geoffe-Ga/adepthood. Verified against the repo state of 2026-07-31.

Prerequisites

• .venv activated, backend requirements installed
• A local PostgreSQL reachable via DATABASE_URL (or the default in backend/src/database.py)
• Migrations live in backend/migrations/ (alembic.ini sets script_location = %(here)s/migrations); migrations/env.py injects the runtime DATABASE_URL, normalized for asyncpg

Steps

1. Write the test first (TDD is required — adepthood AGENTS.md): a failing test that exercises the new column/table through the model or endpoint.

2. Change or add the SQLModel class under backend/src/models/ (one module per table; export it via models/__init__.py so autogenerate sees it).

3. Generate the revision from backend/:

cd backend
alembic revision --autogenerate -m "add <thing>"

1. Review the generated file in backend/migrations/versions/ — autogenerate output is a draft, not a truth. Ensure both upgrade() and downgrade() are correct; follow the existing revision naming style (<hash>_<snake_case_summary>.py).

2. Apply and test:

alembic upgrade head
pytest

Verify

• alembic upgrade head runs cleanly on a fresh database, and alembic downgrade -1 reverses it.
• Your new test passes; the full gate run (quality gates) stays green.