unlock_detector library

Detects device lock/unlock, app foreground/background, idle and screen state — for user online/offline presence.

Platform coverage:

• foreground / background / idle — all platforms. On Android and iOS this tracks the app lifecycle; on web and desktop it tracks window focus/blur (a focused window is foreground, a blurred or minimized one is background).
• locked / unlocked / screenOn — Android and iOS only.