fix(dashboard): remap UUID-keyed chart_configuration entries on import

Dashboards exported via export_example use chart UUIDs as keys in
chart_configuration (and as values in chartsInScope). Extend
update_cross_filter_scoping and helpers to resolve UUID keys/values to
new integer IDs via position data, rather than silently dropping them.
Unknown UUID keys are preserved unchanged as a safe fallback.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>