feat: Account-Screen mit Nutzerprofil, App-Version aus package.json

- AccountScreen zeigt jetzt Profilbild, Anzeigename und @Login des eingeloggten Twitch-Nutzers (via neuem IPC-Kanal twitch:get-own-user)
- CSS: account__avatar zeigt Profilbild, neue Klassen für identity, name, login und error

electron.vite.config.ts

@@ -1,9 +1,30 @@
+import { readFileSync } from 'node:fs'
 import { resolve } from 'node:path'
 import { defineConfig, externalizeDepsPlugin } from 'electron-vite'
 import react from '@vitejs/plugin-react'
 
+interface PackageJson {
+  version?: string
+}
+
+function getAppVersion(): string {
+  try {
+    const pkg = JSON.parse(readFileSync(resolve(__dirname, 'package.json'), 'utf8')) as PackageJson
+    if (pkg.version) return pkg.version
+  } catch {
+    // ignore malformed package.json and use final fallback below
+  }
+
+  return '0.0.0-dev'
+}
+
+const appVersion = getAppVersion()
+
 export default defineConfig({
   main: {
+    define: {
+      'process.env.APP_VERSION': JSON.stringify(appVersion)
+    },
     plugins: [externalizeDepsPlugin()],
     build: {
       rollupOptions: {
@@ -12,6 +33,9 @@ export default defineConfig({
     }
   },
   preload: {
+    define: {
+      'process.env.APP_VERSION': JSON.stringify(appVersion)
+    },
     plugins: [externalizeDepsPlugin()],
     build: {
       rollupOptions: {
@@ -21,6 +45,9 @@ export default defineConfig({
   },
   renderer: {
     root: resolve(__dirname, 'src/renderer'),
+    define: {
+      'process.env.APP_VERSION': JSON.stringify(appVersion)
+    },
     plugins: [react()],
     resolve: {
       alias: {