add tappable PWA install banner, tab bar safe area for notched devices

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/features/onboarding/components/onboarding-form.tsx

@@ -10,7 +10,7 @@ import { dbExec } from "@/shared/hooks/use-db";
 import { GKV_KASSEN } from "@/shared/lib/gkv-kassen";
 import { cn } from "@/shared/lib/utils";
 
-function detectPlatform(): "ios" | "android" | "unknown" {
+export function detectPlatform(): "ios" | "android" | "unknown" {
 	const ua = navigator.userAgent;
 	if (/iPad|iPhone|iPod/.test(ua)) return "ios";
 	if (/Android/.test(ua)) return "android";