Restore the page size control for search results

[PhilReedData]

Describe the bug

The TeSS API supports page_size (or pageSize in the widget). This control is no longer present in the web interface for search results though it works as a GET variable. Request the control is restored.

To Reproduce

Steps to reproduce the behavior:

1. Search results show pages of size 10 only.
2. Add &page_size=5 for example in the search query.

Expected behavior

A drop-down box or equivalent of choice of page sizes, near the list of pages.

Additional context

Discussed at TeSS tech call 2025-12-10