Oracle integration — Price feed module

[nafiuishaaq]

Description:
Integrate with a price oracle (e.g., Band, Chainlink) for fiat or multi-token escrows.

Acceptance Criteria:

set_oracle(oracle_id: Address) admin function.

get_price(asset: Bytes32) -> i128 internal function.

Price validation: timestamp within freshness threshold.

Fallback to admin-provided price if oracle fails.

Unit tests mock oracle responses.

Labels: integration, oracle, price-feed