feat add oracle price feed integration tests

[Obiajulu-gif]

Summary

Related Issue

Closes #

Type of Change

• Bug fix
• New feature
• Refactor / internal improvement
• Documentation update
• Test-only change
• DevOps / CI change

Changes

Testing Performed

Smart Contract Security Checklist

• CEI pattern followed (checks before effects before interactions)
• All arithmetic uses checked operations (checked_add, checked_sub, saturating_*) — no bare + or * without overflow guard
• New state-changing functions have reentrancy guard (non_reentrant_start / non_reentrant_end)
• New admin functions emit events
• No panic!() with string messages — typed errors (PoolError, InvoiceError) used instead
• Storage TTL extended in all functions that touch persistent state
• Fuzz test added or updated for new invariants

Checklist

• Tests added or updated (cargo test / npm test passes)
• Documentation updated (README, inline docs, API reference)
• For security or incident-response changes, at least one core team approval is noted in this PR
• cargo fmt and cargo clippy -- -D warnings pass (if contracts changed)
• npm run lint and npm run build pass (if frontend changed)
• No secrets, private keys, or production contract IDs in code
• API reference updated if contract interface changed
• PR title is descriptive and follows type(scope): description convention
• Smart contract security checklist above completed (if contracts/ changed)

Screenshots (UI changes only)

Closes #418

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