[misc] Replace in deprecation dropped httpx.AsyncClient app arg

[felixT2K]

This PR:

• Replace httpx.AsyncClient removed app=app with transport=ASGITransport(app=app)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.54%. Comparing base (2711df4) to head (c0f5330).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1802   +/-   ##
=======================================
  Coverage   96.54%   96.54%           
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  Files         165      165           
  Lines        7892     7892           
=======================================
  Hits         7619     7619           
  Misses        273      273           

Flag	Coverage Δ
unittests	96.54% <ø> (ø)

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