Add an opt-in setting to hide the Caps Lock indicator

[manovotny]

Summary

macOS shows a Caps Lock indicator in text fields whenever Caps Lock is on. For Capsomnia users that's constant noise — Caps Lock stays on for hours, and the indicator appears even with "Prevent all-caps typing" enabled.

This adds an opt-in "Hide the Caps Lock indicator" toggle to Advanced Settings that suppresses it through the system redesigned_text_cursor feature-flag override.

The override only takes effect after a restart, so the toggle shows a localized reminder until the current boot reflects the on-disk state. Toggling back before restarting clears the reminder, and the state survives app relaunches by comparing against a kern.boottime snapshot.

Changes

• The privileged helper gains argument-restricted indicator-hide and indicator-show modes. They edit only /Library/Preferences/FeatureFlags/Domain/UIKit.plist, preserve unrelated flags in that file, and delete it when nothing else remains. The sudoers rules in install.sh and the pkg postinstall stay argument-exact, now five commands instead of three.
• New toggle in Advanced Settings → System Behavior, localized in all four languages. Its state reads from the on-disk plist rather than UserDefaults, so a failed helper call (for example an install that predates the new sudoers entries) reverts the toggle on reload instead of showing a state that isn't real.
• The uninstaller restores the macOS indicator default before removing the helper.
• Tests cover the plist parsing, the restart-pending policy (including boot-time drift and toggling back), and the new settings row; SECURITY.md and all four READMEs document the new helper modes.

Notes

• Existing installs need ./scripts/install.sh or the next pkg to pick up the new sudoers entries; until then the toggle reverts and logs the denied helper call.
• This overlaps with Add an opt-in Keep display awake setting #88 in the settings window, strings, and tests. Happy to rebase whichever lands second.