feat: PWA-Installation aktiv anbieten, besonders für iPad/iOS.

Zeigt nach dem Login ein Installations-Banner mit Safari-Anleitung oder nativer Install-Schaltfläche und ergänzt iOS-Meta-Tags sowie einen dauerhaften Hinweis in den Einstellungen.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/src/hooks/usePwaInstall.ts

@@ -0,0 +1,90 @@
+import { useState, useEffect, useCallback } from 'react'
+
+const DISMISS_KEY = 'pwa_install_dismissed_until'
+
+interface BeforeInstallPromptEvent extends Event {
+  prompt(): Promise<void>
+  userChoice: Promise<{ outcome: 'accepted' | 'dismissed' }>
+}
+
+export type PwaInstallPlatform = 'ios' | 'android' | 'desktop'
+
+export function isRunningStandalone(): boolean {
+  return (
+    window.matchMedia('(display-mode: standalone)').matches ||
+    window.matchMedia('(display-mode: fullscreen)').matches ||
+    (window.navigator as Navigator & { standalone?: boolean }).standalone === true
+  )
+}
+
+export function isIosDevice(): boolean {
+  const ua = navigator.userAgent
+  if (/iPad|iPhone|iPod/.test(ua)) return true
+  // iPadOS 13+ may report as Mac with touch support
+  return navigator.platform === 'MacIntel' && navigator.maxTouchPoints > 1
+}
+
+function readDismissed(): boolean {
+  try {
+    const until = localStorage.getItem(DISMISS_KEY)
+    if (!until) return false
+    if (until === 'forever') return true
+    return Date.now() < Number(until)
+  } catch {
+    return false
+  }
+}
+
+export function usePwaInstall() {
+  const [deferredPrompt, setDeferredPrompt] = useState<BeforeInstallPromptEvent | null>(null)
+  const [dismissed, setDismissed] = useState(readDismissed)
+  const isStandalone = isRunningStandalone()
+
+  useEffect(() => {
+    const handler = (e: Event) => {
+      e.preventDefault()
+      setDeferredPrompt(e as BeforeInstallPromptEvent)
+    }
+    window.addEventListener('beforeinstallprompt', handler)
+    return () => window.removeEventListener('beforeinstallprompt', handler)
+  }, [])
+
+  const platform: PwaInstallPlatform | null = isIosDevice()
+    ? 'ios'
+    : deferredPrompt
+      ? /Android/i.test(navigator.userAgent)
+        ? 'android'
+        : 'desktop'
+      : null
+
+  const canPrompt = !isStandalone && !dismissed && (platform === 'ios' || !!deferredPrompt)
+
+  const install = useCallback(async (): Promise<boolean> => {
+    if (!deferredPrompt) return false
+    await deferredPrompt.prompt()
+    const { outcome } = await deferredPrompt.userChoice
+    setDeferredPrompt(null)
+    return outcome === 'accepted'
+  }, [deferredPrompt])
+
+  const dismissLater = useCallback(() => {
+    const until = Date.now() + 3 * 24 * 60 * 60 * 1000
+    localStorage.setItem(DISMISS_KEY, String(until))
+    setDismissed(true)
+  }, [])
+
+  const dismissForever = useCallback(() => {
+    localStorage.setItem(DISMISS_KEY, 'forever')
+    setDismissed(true)
+  }, [])
+
+  return {
+    canPrompt,
+    platform,
+    install,
+    dismissLater,
+    dismissForever,
+    isStandalone,
+    hasNativeInstall: !!deferredPrompt
+  }
+}