fix(worker): prevent OperationalError in UploadFinisher from stale DB connection

[sentry]

This PR addresses the OperationalError: (psycopg2.OperationalError) server closed the connection unexpectedly occurring in app.tasks.upload.UploadFinisher.

Root Cause:
UploadFinisher tasks were encountering SoftTimeLimitExceeded or PostgreSQL's idle_in_transaction_session_timeout because DB sessions were held open across long-running non-database operations. This resulted in the database connection being unexpectedly closed, leading to an OperationalError when db_session.commit() was subsequently called on the dead connection.

Changes Made:

1. Reset DB connection in _handle_finisher_lock: After finish_reports_processing completes its potentially long-running operations, a db_session.rollback() is now explicitly called. This releases the potentially stale connection back to the pool. With pool_pre_ping enabled, the next database operation will acquire a fresh or validated connection, preventing errors from idle timeouts.
2. Commit commit.state = "skipped" immediately: In finish_reports_processing, the commit.state = "skipped" change (for CI skip tags) is now immediately followed by a db_session.commit(). This ensures the change is persisted to the database before the db_session.rollback() in the calling function can discard it.

These changes ensure proper management of database connections around intensive processing, mitigating connection timeouts and operational errors.

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Fixes WORKER-Z7D

_{This PR was automatically generated by Sentry. You can adjust this setting at any time.}

[thomasrockhu-codecov]

✨ Harness AI Code Review

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✅ Risk: LOW

This PR mitigates the OperationalError in UploadFinisher by rolling back the DB session after the long-running finish_reports_processing call (releasing a potentially stale connection so pool_pre_ping can revalidate it), and by committing commit.state = "skipped" immediately in the CI-skip branch so it survives that rollback. The change is well-scoped: all DB mutations that precede the rollback are already committed — the report save commits at _process_reports_with_lock, mark_uploads_as_merged is Redis-only, and the notify/skip branches each commit their own ORM writes — so the new rollback discards no pending work.

No issues found above the confidence threshold.

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 91.63%. Comparing base (17e0f08) to head (cff597b).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
apps/worker/tasks/upload_finisher.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2155      +/-   ##
==========================================
- Coverage   91.63%   91.63%   -0.01%     
==========================================
  Files        1337     1337              
  Lines       53262    53265       +3     
  Branches     1647     1647              
==========================================
+ Hits        48805    48807       +2     
- Misses       4136     4137       +1     
  Partials      321      321              

Flag	Coverage Δ
workerintegration	58.49% <66.66%> (+<0.01%)	⬆️
workerunit	90.54% <66.66%> (-0.01%)	⬇️

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Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
apps/worker/tasks/upload_finisher.py	66.66%	1 Missing ⚠️

❌ Your patch check has failed because the patch coverage (66.66%) is below the target coverage (90.00%). You can increase the patch coverage or adjust the target coverage.

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