Refs #8933: wire onboarding format upgrade

[T-rav]

Summary

• add an onboarding draft format-upgrade endpoint that writes a standards snapshot and opens a PR against the draft staging branch
• wire the dashboard Upgrade format action through context state and ProjectView feedback
• cover route registration, preconditions, PR creation, reducer updates, and UI success/failure states

Tests

• uv run pytest tests/test_onboarding_api.py -q
• npm test -- --run src/components/tests/ProjectView.test.jsx src/context/tests/HydraFlowContext.test.jsx
• make quality