Add status menu maintenance actions

[yvette-carlisle]

Summary

• add Open Screenshots Folder to the menu bar menu
• add Check for Updates… to the menu bar menu using the existing Sparkle flow
• update the Settings/status-menu spec

Validation

• cargo make fmt-swift
• cargo make lint-swift
• cargo make test-macos-native-host
• cargo make test-macos-native-host-stage
• git diff --check
• semantic drift audit: pass