fix: Isolate cleanup steps in Actor __aexit__ to prevent cascading failures

[vdusek]

Summary

• Wrap each cleanup step in finalize() (event_manager.__aexit__, _charging_manager_implementation.__aexit__, _save_actor_state) with independent try/except blocks
• Previously, if event_manager.__aexit__() raised, charging manager exit and state persistence were skipped entirely
• Failures are now logged and don't prevent subsequent cleanup steps from executing

Test plan

• Existing unit tests pass (182/182)
• Verify cleanup resilience by injecting a failure in one cleanup step and confirming others still run

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.31%. Comparing base (1610d0d) to head (34d3836).
⚠️ Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
src/apify/_actor.py	50.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #842      +/-   ##
==========================================
- Coverage   86.40%   86.31%   -0.10%     
==========================================
  Files          48       48              
  Lines        2906     2915       +9     
==========================================
+ Hits         2511     2516       +5     
- Misses        395      399       +4     

Flag	Coverage Δ
e2e	37.94% <0.00%> (-0.12%)	⬇️
integration	59.38% <50.00%> (-0.09%)	⬇️
unit	74.33% <50.00%> (-0.06%)	⬇️

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