OZ native yield audit combined fixes

[kyzooghost]

This PR implements issue(s) #

Checklist

• I wrote new tests for my new core changes.
• I have successfully ran tests, style checker and build against my new changes locally.
• I have informed the team of any breaking changes if there are any.

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Note

Moves staking pause/unpause event emission into internal _pauseStaking/_unpauseStaking so internal callers also emit, and updates tests to expect the pause event during ossification initiation.

• Contracts (contracts/contracts/yield/YieldManager.sol):
  • Emit YieldProviderStakingPaused and YieldProviderStakingUnpaused from internal helpers (_pauseStaking, _unpauseStaking) instead of external pauseStaking/unpauseStaking.
• Tests (contracts/test/yield/unit/YieldManager.controls.ts):
  • Update ossification initiation test to expect YieldProviderStakingPaused when calling initiateOssification.

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