WryActivity's generated back handler calls WebView.goBack(), which does NOT
dispatch popstate for same-document history.pushState() entries — so the OS back
gesture never reached the app's popstate handler and couldn't dismiss modals
(new product, add-to-eaten, ЧЗ scanner) or navigate screens; only the on-screen
back arrow worked. WryActivity.kt is auto-regenerated each build, so override in
the app-owned MainActivity instead: set handleBackNavigation=false and register
our own OnBackPressedCallback that runs window.history.back() via evaluateJavascript,
which fires popstate. Verified on-device: swipe-back now closes modals and the ЧЗ
scanner. (adb `input keyevent BACK` does NOT go through OnBackPressedDispatcher on
Android 13+, so it can't be used to test this — only the real gesture does.)