Prevent submit reentry while busy

[Jim8y]

Summary

• ignore spinner button clicks while the control is already in its busy state
• prevent async submit handlers from being invoked again before the previous operation finishes

Validation

• MD_APPLE_SDK_ROOT=/Applications/Xcode-26.5.0.app dotnet build OneGateApp/OneGateApp.csproj -f net10.0-ios -p:RuntimeIdentifier=iossimulator-arm64 -p:EnableCodeSigning=false -p:CodesignKey= -p:CodesignProvision= -p:ProvisioningType=automatic
• dotnet test OneGate.DebugProtocol.Tests/OneGate.DebugProtocol.Tests.csproj

[Copilot]

Pull request overview

This PR prevents SpinnerButton click reentry by ignoring click events while the control is already in its busy state, helping ensure async submit handlers aren’t invoked concurrently.

Changes:

• Add a guard in SpinnerButton’s click handler to no-op when IsBusy is true.

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