fix: Guard ReentrantLock against None task context

[vdusek]

Summary

• Add a runtime guard in ReentrantLock to raise RuntimeError when asyncio.current_task() returns None, preventing the lock from being silently bypassed due to None is None evaluating to True.

Test plan

• Verify uv run poe check-code passes
• Confirm ReentrantLock raises RuntimeError when called outside an asyncio.Task

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 86.48%. Comparing base (1610d0d) to head (d88d00e).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/apify/_utils.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@ Coverage Diff @@ ## master #841 +/- ## ========================================== + Coverage 86.40% 86.48% +0.07%  ========================================== Files 48 48 Lines 2906 2908 +2 ========================================== + Hits 2511 2515 +4  + Misses 395 393 -2 

Flag	Coverage Δ
e2e	38.03% <0.00%> (-0.03%)	⬇️
integration	59.45% <0.00%> (-0.01%)	⬇️
unit	74.44% <50.00%> (+0.05%)	⬆️

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.

[janbuchar]

LGTM