fix: resolve merge conflicts with main

- Adopt main's getRunningQueriesCount endpoint (SQL aggregation) for overview polling
- Remove getRunningQueriesOverview endpoint (superseded by main's count endpoint)
- Keep SELECT * and normalizeQueryResult for detailed running queries table
- Use main's useQueriesActivityData with useGetRunningQueriesCountQuery

Co-authored-by: astandrik <8037318+astandrik@users.noreply.github.com>

Author: Copilot