initInactivityWatcher() was called once at startup and returned early if
screensaver was disabled at that moment. Enabling it later from the
settings panel had no effect until page reload.
- Make initInactivityWatcher() idempotent: attach DOM listeners only once
(flag _inactivityListenersAttached), check screensaver_enabled dynamically
inside each handler so disabling/enabling is reflected immediately
- Call initInactivityWatcher() at end of saveSettings() so the inactivity
timer starts immediately when user enables screensaver
dadaloop82
6f19d1bcd5