The Dockerfile runs `alembic stamp --purge base && alembic upgrade head`
on every restart, so all migrations re-run against an existing database.
Migration 0004 used `op.add_column()` which fails on re-run with
"column already exists". Migration 0005 used `op.create_table()` which
would fail similarly.
Both now use raw SQL with idempotency guards:
- 0004: `DO $$ BEGIN ALTER TABLE ADD COLUMN ... EXCEPTION WHEN
duplicate_column` + `IF EXISTS` check before touching the tasks table
- 0005: `CREATE TABLE IF NOT EXISTS` + `CREATE INDEX IF NOT EXISTS`
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
bvandeusen
b761db4c44