Fix System One score legend labels

[webdevtodayjason]

Problem

/v1/systemone built score legends from criteria keys, so labelled levels such as {"0": "Calm"} returned {"0": "0"} instead of the display label the caller sent.

Decision

Preserve score display labels during question translation and use them only for the outbound legend. Criteria keys remain the source for model options, selected-level lookup, probabilities, and expected-score arithmetic.

Proof

• .venv/bin/pytest -q tests/test_systemone.py: 53 passed
• .venv/bin/pytest -q tests/: 3243 passed, 2 skipped, 1 xfailed, with one unrelated free-space timing assertion that passed immediately when rerun alone
• .venv/bin/pytest -q tests/test_download_fit.py::test_free_space_is_measured_on_the_nearest_parent_that_exists: 1 passed
• .venv/bin/ruff check: all checks passed

Changelog: Fixed /v1/systemone score legends to return criteria labels instead of level keys.

Fixes #288

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