Bugfix/needs stories sprint label scope

[Juce-me]

Summary

• Fix Needs Stories / Backlog alert scope so selected future sprint labels are considered when deciding whether an epic belongs to the selected planning sprint.
• Route Needs Stories alert grouping through configured team labels instead of relying only on the Jira Team field.
• Pass configured team labels from the ENG frontend task loader to the backend task endpoint.
• Include team label scope in the task cache key so different planning-team scopes cannot reuse stale alert payloads.

Validation

• npm run build
• .venv/bin/python -m unittest discover -s tests
• node --test tests/test_*.js
• Live Basic-auth route check confirmed the referenced label-scoped epics are included in the alert payload.