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/vite.config.ts

@@ -2,9 +2,10 @@
 import { defineConfig } from 'vite'
 import react from '@vitejs/plugin-react'
 import { VitePWA } from 'vite-plugin-pwa'
-import { readFileSync } from 'node:fs'
+import { readFileSync, writeFileSync } from 'node:fs'
 import { resolve, dirname } from 'node:path'
 import { fileURLToPath } from 'node:url'
+import type { Plugin } from 'vite'
 
 const __dirname = dirname(fileURLToPath(import.meta.url))
 
@@ -19,6 +20,19 @@ function readAppVersion(): string {
   }
 }
 
+function versionJsonPlugin(version: string): Plugin {
+  return {
+    name: 'version-json',
+    writeBundle(options) {
+      const outDir = options.dir ?? resolve(__dirname, 'dist')
+      writeFileSync(
+        resolve(outDir, 'version.json'),
+        `${JSON.stringify({ version }, null, 2)}\n`
+      )
+    }
+  }
+}
+
 // https://vite.dev/config/
 export default defineConfig({
   test: {
@@ -42,6 +56,7 @@ export default defineConfig({
   },
   plugins: [
     react(),
+    versionJsonPlugin(readAppVersion()),
     VitePWA({
       strategies: 'injectManifest',
       srcDir: 'src',