Fix atomic proof finalization

[Devadakene]

Closes #52

Description

Fixes a critical race condition where a single proof could be finalized multiple times by independent actors (auto-verification worker, admin review, and quorum validators), which resulted in duplicated RewardPayout rows, double notifications, and leaked task completion slots.

To address this, the finalization logic has been extracted into a single shared service (src/services/proofFinalizationService.ts). We replaced the vulnerable updateMany approach with an atomic SELECT ... FOR UPDATE query at the start of the finalization transaction, which serializes concurrent requests. Additionally, state-based access control was implemented (via expectedStatuses) to strictly enforce which statuses can be finalized by which actors, preventing admins from finalizing proofs that are currently being processed by the verification worker.

Fixes #52

Type of Change

• Bug fix (non-breaking change fixing an issue)
• New feature (non-breaking change adding functionality)
• Breaking change (fix or feature that breaks existing behaviour)
• Refactor (code change that neither fixes a bug nor adds a feature)
• Test (adding or updating tests)
• Docs (documentation-only changes)
• Chore (tooling, CI/CD, build process)

How Has This Been Tested?

• npm test passes
• npm run build succeeds
• Manual testing steps described below

A new concurrency integration test tests/integration/proofFinalization.test.ts was added to fire all three actors simultaneously. It asserts that only one actor succeeds while producing exactly one Verification row, one RewardPayout row, and incrementing the task's completion count by exactly 1.

Checklist

• My code follows the project's coding conventions
• I have added tests that prove my fix/feature works
• New and existing tests pass locally
• I have updated the documentation if needed
• My changes generate no new warnings or errors

Additional Context

• The integration test ensures exact-once slot claim semantics when all three paths fire in parallel.
• reviewProof, verificationWorker, and resolveQuorum now share the identical finalization code path instead of relying on their own separate DB interactions.

[cybermax4200]

The ci checks are failing please fix them