feat: stabilize admin dashboard, refactor group management, implement PWA, and fix routing

app/middleware/admin.ts

@@ -1,15 +1,15 @@
 export default defineNuxtRouteMiddleware((to, from) => {
   const token = useCookie('xflow_token')
-  if (!token.value) {
-    return navigateTo('/login')
-  }
+  
+  if (!token.value) return navigateTo('/login')
 
   try {
-    const payload = JSON.parse(atob(token.value.split('.')[1]))
-    if (payload.role !== 'admin') {
-      return navigateTo('/')
-    }
-  } catch {
+    const base64Url = token.value.split('.')[1]
+    const base64 = base64Url.replace(/-/g, '+').replace(/_/g, '/')
+    const payload = JSON.parse(window.atob(base64))
+    
+    if (payload.role !== 'admin') return navigateTo('/')
+  } catch (e) {
     return navigateTo('/login')
   }
 })