Frontend: Composables useConfirm/useChat/usePolling; Guide-Chat abbrechbar

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/composables/usePolling.js

@@ -0,0 +1,44 @@
+import { onUnmounted } from 'vue'
+
+// Polling mit Visibility-Pause: Tab unsichtbar → stoppen; wieder sichtbar →
+// sofortiger Tick, dann weiter, falls isActive(). Stoppt selbst, sobald
+// isActive() nach einem Tick false liefert.
+export function usePolling(tick, isActive, interval = 3000) {
+  let timer = null
+
+  function stop() {
+    if (timer) {
+      clearInterval(timer)
+      timer = null
+    }
+  }
+
+  function start() {
+    stop()
+    timer = setInterval(async () => {
+      await tick()
+      if (!isActive()) stop()
+    }, interval)
+  }
+
+  function running() {
+    return !!timer
+  }
+
+  async function onVisibility() {
+    if (document.hidden) {
+      stop()
+    } else {
+      await tick()
+      if (isActive()) start()
+    }
+  }
+
+  document.addEventListener('visibilitychange', onVisibility)
+  onUnmounted(() => {
+    stop()
+    document.removeEventListener('visibilitychange', onVisibility)
+  })
+
+  return { start, stop, running }
+}