Add instance state change support via setInstanceOperation API

[Chr0nicl3]

• Add setInstanceOperation() to InstanceService for ENABLE/DISABLE/EVACUATE with reason and audit trail (instanceOperationSource=USER)
• Add showInput() to HelperService using InputDialogComponent for collecting reason before state changes
• Refactor enableInstance/disableInstance to use setInstanceOperation, add evacuateInstance method to InstanceDetailComponent
• Expand admin menu with Enable/Disable/Evacuate options, each prompting for a reason before executing
• Add unit tests for setInstanceOperation service method and component

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