test: bound serve_in_thread startup to prevent CI hangs

[vdusek]

Description

The session-scoped http_server fixture uses unused_tcp_port_factory() to pick a port, then starts uvicorn in a background thread. When another xdist worker grabs that port before this fixture's bind() runs, the server thread fails with [Errno 98] address already in use and exits without ever setting server.started = True. The startup poll loop in serve_in_thread had no timeout, so it spun forever and pytest-timeout killed the whole worker 30 minutes later — marking every queued test on that worker as a timeout error.

This is a companion to #1892, which bounded the teardown; the same class of bug lived in the startup.

Fix

In serve_in_thread, bound the wait with:

1. A 30s deadline (time.monotonic() based).
2. A thread.is_alive() check that detects when uvicorn has exited (bind failure being the realistic cause).

Either condition raises a RuntimeError with a descriptive message, so the fixture fails fast and the failing test surfaces a clear error instead of a 30-minute hang.

Observed failure

https://github.com/apify/crawlee-python/actions/runs/25895087554/job/76106390899

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.83%. Comparing base (4023314) to head (490a4a3).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1897      +/-   ##
==========================================
- Coverage   92.86%   92.83%   -0.03%     
==========================================
  Files         167      167              
  Lines       11699    11699              
==========================================
- Hits        10864    10861       -3     
- Misses        835      838       +3     

Flag	Coverage Δ
unit	92.83% <ø> (-0.03%)	⬇️

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[Mantisus]

LGTM