On-chain oracle failure testing

[UlyanaAndrukhiv]

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Context

Some tests currently rely on a mock oracle implementation to simulate price updates and validate protocol behavior. While these tests are useful for controlled scenarios, they do not demonstrate how the system behaves with the actual on-chain oracle implementations.

To improve test coverage and confidence in production behavior, we should add tests that use the existing on-chain oracles, such as the Band oracle or Pyth oracle, instead of relying only on mocks.