fix(pwa): Updates zuverlässiger erkennen und veraltete Instanzen automatisch reparieren

Unabhängige version.json-Prüfung, häufigere Update-Checks und Hard Recovery
beheben hängende Android-PWAs ohne manuelles Cache-Löschen.

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

client/src/services/pwaVersion.ts

@@ -0,0 +1,59 @@
+const APP_VERSION =
+  typeof __APP_VERSION__ !== 'undefined' ? __APP_VERSION__ : '0.0.0.0-dev'
+
+export function getAppVersion(): string {
+  return APP_VERSION
+}
+
+export function parseAppVersion(version: string): number[] {
+  return version
+    .replace(/^v/i, '')
+    .split('.')
+    .map((part) => Number.parseInt(part, 10) || 0)
+}
+
+/** Positive when `a` is newer than `b`. */
+export function compareAppVersions(a: string, b: string): number {
+  const partsA = parseAppVersion(a)
+  const partsB = parseAppVersion(b)
+  const length = Math.max(partsA.length, partsB.length)
+
+  for (let index = 0; index < length; index += 1) {
+    const diff = (partsA[index] ?? 0) - (partsB[index] ?? 0)
+    if (diff !== 0) return diff
+  }
+
+  return 0
+}
+
+export function isNewerAppVersion(serverVersion: string, clientVersion: string): boolean {
+  return compareAppVersions(serverVersion, clientVersion) > 0
+}
+
+export async function fetchDeployedVersion(timeoutMs = 4_000): Promise<string | null> {
+  if (!navigator.onLine) return null
+
+  const controller = new AbortController()
+  const timeoutId = window.setTimeout(() => controller.abort(), timeoutMs)
+
+  try {
+    const response = await fetch(`/version.json?_=${Date.now()}`, {
+      cache: 'no-store',
+      signal: controller.signal
+    })
+    if (!response.ok) return null
+
+    const payload = (await response.json()) as { version?: unknown }
+    return typeof payload.version === 'string' ? payload.version.trim() : null
+  } catch {
+    return null
+  } finally {
+    window.clearTimeout(timeoutId)
+  }
+}
+
+export async function isDeployedVersionNewer(): Promise<boolean> {
+  const deployedVersion = await fetchDeployedVersion()
+  if (!deployedVersion) return false
+  return isNewerAppVersion(deployedVersion, getAppVersion())
+}