Fix schema init order: run user_id migration before index creation

The ALTER TABLE migration for user_id must run before the index on
projects(user_id) is created, otherwise existing databases fail with
"no such column: user_id".

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Use Docker Hub (budstudio/taskgraph) for Docker image

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>