Fix/orphan proofs sweeper

[Devadakene]

Closes #79

Description

This PR introduces a recovery sweeper to handle PENDING proofs that become permanently stuck. Previously, if enqueueVerification failed and the subsequent database rollback transaction also failed, the proof would remain in a PENDING state forever without a corresponding verification job.

This change adds recoverOrphanedProofs to taskService.ts which automatically detects orphaned proofs older than a configurable threshold (PROOF_ORPHAN_MAX_AGE_MS, defaulting to 30 minutes) and escalates them by rejecting them with a system failure note. The sweeper is integrated into expiryWorker.ts to run periodically.

Fixes #5 (and addresses the related permanently-stuck proofs rollback issue).

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
  (Added unit tests in taskService.test.ts to verify orphaned proof detection and rejection, and updated expiryWorker.test.ts to ensure the sweeper is called on schedule).

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 max age for an orphaned proof is controlled by the PROOF_ORPHAN_MAX_AGE_MS environment variable, which defaults to 30 minutes (1800000 ms).
• Auto-rejected orphaned proofs will have their status updated to REJECTED and a verification note appended reading: "Proof orphaned due to system failure".

[cybermax4200]

The ci checks are failing please fix them