[codex] Improve seckill flow reliability

[Rutilated]

Summary

• improve task log streaming, task status recovery, and localhost server defaults
• make Taobao order confirmation detection submit-aware and failure-aware
• make JD reservation checkout refresh the cart, locate the configured target product, and continue through order submission
• add unit tests for Taobao/JD flow behavior and task failure status

Validation

• .venv\Scripts\python.exe -m unittest discover -s tests -p 'test_*.py' -v
• .venv\Scripts\python.exe -m compileall app.py seckill.py
• C:\Users\Rutilate\.cache\codex-runtimes\codex-primary-runtime\dependencies\node\bin\node.exe --check static/js/seckill.js