Fix alembic migration path resolution

[danielmillerp]

Summary

• Fix env.py project root path from ../../../.. (resolves to /) to ../../.. (resolves to /app)
• This was causing ModuleNotFoundError: No module named 'src' at pod startup, preventing alembic upgrade head from running
• As a result, the checkpoints table (from migration d1a6cde41b3f) was never created on AWS dev, breaking LangGraph agents

Context

The OTel auto-instrumentation init container overrides PYTHONPATH to /otel-auto-instrumentation-python/..., so the Dockerfile's ENV PYTHONPATH=/app is lost. env.py compensates by explicitly adding the project root to sys.path, but was resolving 4 levels up (/) instead of 3 (/app).

Test plan

• Verify alembic upgrade head runs successfully on pod startup (check logs for Added /app to Python path and Migration completed successfully)
• Verify checkpoints table exists after deployment
• Verify LangGraph agents can use the checkpoint endpoint without 500 errors

🤖 Generated with Claude Code