fix(ui): clear KMS settings when toggling to Public privacy mode

[QueenColly]

Summary
This PR resolves #435 by fixing a state inconsistency bug in the SPV Wizard's privacy step. Previously, switching from KMS back to Public left orphaned KMS data in the state. The onChange handler has been updated to explicitly nullify KMS-specific fields whenever the Public option is selected.

Changes Proposed

Updated SPVPrivacyStep.tsx to intercept the privacy mode toggle event.

Added state cleanup logic to wipe kmsProvider, kmsKeyId, and kmsRegion when switching to public.

Acceptance Criteria Checklist

[x] Clear KMS-specific settings if user switches back to Public.

[x] State remains consistent and clean without orphaned payload data.

Closes #435

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[Tybravo]

@QueenColly

Please fix the CI Build and Check errors

Thanks