fix(scrapy): Close AsyncThread on scheduler open() failure

[vdusek]

Summary

• Close AsyncThread in the except block of ApifyScheduler.open() before re-raising, preventing a thread leak when open_rq() fails (Scrapy only calls close() after a successful open()).

Test plan

• CI passes

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 85.85%. Comparing base (69b8af9) to head (7113598).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/apify/scrapy/scheduler.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #820      +/-   ##
==========================================
- Coverage   85.92%   85.85%   -0.07%     
==========================================
  Files          46       46              
  Lines        2778     2779       +1     
==========================================
- Hits         2387     2386       -1     
- Misses        391      393       +2     

Flag	Coverage Δ
e2e	37.06% <0.00%> (-0.02%)	⬇️
integration	58.58% <0.00%> (-0.06%)	⬇️
unit	73.40% <0.00%> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.