Add version number display to UI header

Inject app version (v1.0.0) at build time via Vite define config
and display it below the title in muted text.

app/vite.config.ts

@@ -5,6 +5,9 @@ import react from '@vitejs/plugin-react'
 // https://vite.dev/config/
 export default defineConfig({
   plugins: [react()],
+  define: {
+    __APP_VERSION__: JSON.stringify('1.0.0'),
+  },
   server: {
     allowedHosts: ['soos'],
   },