refactor: better query for user counts

[marius-mather]

Description

Rework functions that count users (based on query params) - use dedicated query logic that just counts user IDs instead of selecting the whole user table.

Changes

• Rework query in UserQueryParams.get_count()
• Add unit test for counts

Checklist

• I have commented my code, particularly in hard-to-understand areas
• I have added unit / integration tests that prove my fix is effective or that my feature works
• I have run all tests locally and they pass
• I have updated the documentation (if applicable)
• For any new secrets, I have updated the shared spreadsheet and the GitHub Secrets.

How to Test Manually (if necessary)

Run uv run pytest

[Copilot]

Pull request overview

Refactors admin user-counting logic to run a dedicated COUNT() query instead of selecting full user rows, and adds a regression test to ensure the current admin user is excluded from pagination totals.

Changes:

• Reworked UserQueryParams.get_count() to issue a direct SELECT COUNT(user_id) with existing permission/filter conditions.
• Added an admin API test covering /admin/users/pages totals with exclusion of the current admin user across pagination and approval-status filters.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
routers/admin.py	Updates UserQueryParams.get_count() to use a direct COUNT() statement with existing permission/filter predicates.
tests/admin_api/test_admin.py	Adds regression coverage for /admin/users/pages to ensure the current admin user is excluded from counts.

[amandazhuyilan]

Nice logic change! Hopes this makes the query faster