Scroll trail results to the top whenever filters change

## Problem

When the user changes the selected regions or switches the **Name / Distance / Rating** filter, the trail results update but keep the previous scroll position. This can leave the user partway down a newly filtered or reordered list, requiring a manual scroll back to the top.

## Expected behavior

Reset the trail results list to the top every time either the region selection or the **Name / Distance / Rating** selection changes.

## Acceptance criteria

- Selecting or deselecting a region returns the results list to the top.
- Switching between Name, Distance, and Rating returns the results list to the top.
- The behavior works from any existing scroll position.
- The top item shown belongs to the newly filtered or reordered results.