test: bound serve_in_thread teardown to prevent CI hangs

[vdusek]

The session-scoped http_server fixture's teardown in tests/unit/server.py called thread.join() with no timeout. When uvicorn occasionally fails to honor should_exit (it's stuck inside the asyncio loop's selector poll), the join blocks indefinitely — pytest-timeout eventually kills the run after 30 minutes, taking down the whole job.

The fix bounds the teardown:

1. thread.join(timeout=10) — wait for graceful shutdown.
2. If still alive, set server.force_exit = True and thread.join(timeout=5) — uvicorn's documented hard-exit path.
3. Mark the worker thread as daemon=True so an abandoned thread cannot keep the interpreter alive at process exit.

Observed failure: https://github.com/apify/crawlee-python/actions/runs/25720617454/job/75520659980

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.84%. Comparing base (0e7402f) to head (e1fec6b).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1892      +/-   ##
==========================================
+ Coverage   92.82%   92.84%   +0.01%     
==========================================
  Files         167      167              
  Lines       11699    11699              
==========================================
+ Hits        10860    10862       +2     
+ Misses        839      837       -2     

Flag	Coverage Δ
unit	92.84% <ø> (+0.01%)	⬆️

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