Add insightsExcludeMetrics to the User schema and apply the list as
a feature-payload filter inside /api/insights/generate before
JSON.stringify. The Coach settings PUT mirrors its excludeMetrics
onto the new column so both surfaces share a single privacy
contract — no separate Insights settings panel needed.
Anthropometrics is special-cased to strip only height / age / gender
inside features.context, leaving the aggregate totals intact.