Login POST returns 500 on production

[mathemage]

Summary

Posting the login form on https://deep-workflow.vercel.app/login/?next=/ returns a 500 error in production.

Reproduction

1. Open /login/?next=/ on production
2. Submit the login form
3. Observe Server Error (500)

Goal

Identify the failing auth path, implement a fix, and ship it with regression coverage.

[mathemage]

Confirmed root cause from the Vercel deployment logs: production builds are missing DATABASE_URL.

The merged guard in PR #29 now fails fast with:

DATABASE_URL is required for Vercel production builds. Add it to that environment in Vercel project settings, then redeploy.

The current production deployment is still the older commit (12715cb), which continues to return readiness 503 and login 500 while the production database env is absent.

[mathemage]

Additional live-site evidence from authenticated Vercel access:

• Production env vars currently configured: only DJANGO_SECRET_KEY
• Preview env vars currently configured: only DJANGO_SECRET_KEY
• Current production runtime error: Django falls back to SQLite and login POST crashes with django.db.utils.OperationalError: unable to open database file
• Current main deployment failure: the new guard fails the Vercel build with DATABASE_URL is required for Vercel production builds

Required recovery step

Restore a valid PostgreSQL DATABASE_URL in the Vercel project for Production (and ideally Preview), then redeploy main.

Once the env var exists, the merged change on main will let the deployment proceed only if the database is actually reachable.