Fix iOS Safari auth loops and simplify admin dashboard

- Add session check throttling in useAuth to prevent iOS Safari authentication loops
- Simplify admin dashboard by removing complex system metrics and stats
- Remove system-metrics utility and streamline stats API endpoint
- Update admin interface to focus on core user and role management

composables/useAuth.ts

@@ -150,9 +150,24 @@ export const useAuth = () => {
     }
   };
 
-  // Check authentication status
+  // Session check throttling to prevent iOS Safari loops
+  const lastSessionCheck = ref(0);
+  const SESSION_CHECK_THROTTLE = 5000; // 5 seconds minimum between checks
+  
+  // Check authentication status with debouncing
   const checkAuth = async () => {
+    const now = Date.now();
+    
+    // Throttle session checks to prevent iOS Safari loops
+    if (now - lastSessionCheck.value < SESSION_CHECK_THROTTLE) {
+      console.log('🚫 Session check throttled, using cached result');
+      return !!user.value;
+    }
+    
     try {
+      console.log('🔄 Performing throttled session check...');
+      lastSessionCheck.value = now;
+      
       const response = await $fetch<{
         authenticated: boolean;
         user: User | null;