Reject an all-zero proof hash on submission

[RUKAYAT-CODER]

Background

submit_proof accepts any BytesN<32> as the proof hash, including the all-zero value, which is an obvious placeholder rather than a real proof. Reject an all-zero proof hash with Error::InvalidProofHash so empty/placeholder submissions cannot be stored.

Files to modify (2)

• contracts/earn-quest/src/submission.rs
• contracts/earn-quest/src/validation.rs

Acceptance Criteria

• Implemented across the listed files
• Unit/integration tests added or updated and passing
• No regression; follows project coding standards

[Ranjeet2063]

Hello! I'd like to work on this issue.

Execution Plan for Reject an all-zero proof hash on submission:

• Clean Implementation: Deliver an idiomatic solution for Reject an all-zero proof hash on submission adhering strictly to EarnQuestOne/stellar_Earn's architecture.
• Automated Tests: Provide full test coverage asserting both edge cases and core workflows.
• Clean Git Hygiene: Atomic conventional commits with zero merge conflicts.

Why assign me?

• Proven Proof-of-Work: Implement Wallet Connection System #1 contributor on Mova Store (28 merged Web3 PRs) and official ElizaOS contributor.
• Fast Turnaround: Dedicated to shipping a tested, production-grade PR within 12–24 hours.
• Zero Maintainer Burden: Self-documenting code with green CI and tests included so you don't spend time debugging.

Ready to deliver within 12–24h—please feel free to assign it to me!

[ZacLou]

I’ll add a shared check for the all-zero BytesN<32> proof hash and route submit_proof through it with Error::InvalidProofHash, then cover rejection and the existing valid-path acceptance in focused tests. I’ll keep the change scoped to submission.rs, validation.rs, and their tests, and run the contract test suite before opening a PR.