[GrantFox][High] Enforce oracle freshness before market settlement

[greatest0fallt1me]

Summary

Enforce oracle freshness before market settlement

Why this matters

Settlement must not use stale, missing, or contradictory price data.

Scope

Add explicit freshness, quorum, deviation, and fallback checks with auditable rejection reasons.

Acceptance criteria

• Stale data cannot settle a market.
• Quorum and deviation boundaries are deterministic.
• Fallback behavior is explicit and safe.
• Tests cover outage, recovery, invalid prices, and clock skew.

Validation

Add regression coverage for existing behavior, failure modes, authorization boundaries, and compatibility. The implementation must pass the repository CI checks.

Non-goals

• Typo-only, formatting-only, or documentation-only changes.
• Unrelated refactors or dependency upgrades.
• Weakening existing security, authorization, CI, or production safeguards.

Contributor application

Before implementation, comment with relevant experience, a 1–4 bullet approach, and an estimate for opening the first draft PR. Wait for maintainer assignment before coding.

PR requirements

Use a feature branch, include Closes #<issue-number>, check every acceptance criterion, link criteria to code/tests, explain security and failure-mode considerations, and pass CI.

Reward-readiness

This is a substantive GrantFox campaign issue. Merge and CI success do not by themselves guarantee reward eligibility; final reward-readiness is determined by campaign review.

[arisu6804]

Please consider assigning this issue to me, as I’m prepared to contribute wherever it’s needed, whether that involves protocol logic, interface creation, service-layer development, visual implementation, or cross-component coordination.

[grantfox-oss]

🦊 GrantFox — @arisu6804 has been assigned to this issue as part of the Third Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #900)
2. Your PR will be reviewed by the Predictify-org maintainers

Good luck! Track your progress on GrantFox.

[arisu6804]

I will add a pure oracle admission guard and a settlement wrapper that runs it before any market mutation. The policy will enforce freshness, bounded clock skew, source uniqueness, quorum, deterministic median/deviation checks, and an explicit safe fallback path. Tests will cover outage, recovery, invalid prices, boundaries, and audit-stable rejection decisions.