🐛 Fixed back navigation from post analytics member filters (#28252)

fixes https://linear.app/ghost/issue/BER-3534/issue-when-navigating-back-to-post-analytics-from-filtered-member-view

The Growth member drilldown was marked as a cross-app navigation even though the members route is handled by the same admin router, causing URL normalization to add an extra history entry before returning to analytics.