Returns paginated insight history for the authenticated user.
All insight records are returned as-is — no suspend/expired filtering and no deduplication is applied. Insights are grouped by fixture: each fixture in the response contains an insights[] array, and one fixture can appear with more than one insight (e.g. processed by multiple models or runs).
Pagination operates at the insight level: per_page controls the maximum number of insight records returned, so the number of fixtures per page varies.