Fix redirect loops and SSR hydration issues in auth flow

- Replace ref with useState in useAuth for SSR compatibility
- Move navigation logic from top-level to onMounted hooks
- Add guest middleware to login page to prevent auth conflicts
- Simplify dashboard auth checks by relying on middleware
- Add loading state to index page during auth resolution

This prevents infinite redirect loops and hydration mismatches that
occurred during server-side rendering when navigating between
authenticated and unauthenticated states.

pages/dashboard/index.vue

@@ -18,35 +18,26 @@
 
 <script setup lang="ts">
 definePageMeta({
-  middleware: 'auth'
+  middleware: 'auth',
+  layout: 'dashboard'
 });
 
-const { user, userTier, isAuthenticated, checkAuth } = useAuth();
+const { user, userTier } = useAuth();
 const loading = ref(true);
-const authChecked = ref(false);
 
-// Check authentication on mount
-onMounted(async () => {
-  console.log('🔄 Dashboard mounted, checking authentication...');
+// Route to tier-specific dashboard - auth middleware ensures user is authenticated
+onMounted(() => {
+  console.log('🔄 Dashboard mounted, routing to tier-specific page...');
   
-  // Ensure auth is checked before routing
-  await checkAuth();
-  authChecked.value = true;
-  
-  console.log('✅ Auth check complete:', { 
-    isAuthenticated: isAuthenticated.value, 
-    user: user.value?.email,
-    tier: userTier.value 
-  });
-  
-  // Now route based on auth status
-  if (isAuthenticated.value && user.value) {
+  // Auth middleware has already verified authentication - just route to tier page
+  if (user.value && userTier.value) {
     const tierRoute = `/dashboard/${userTier.value}`;
     console.log('🔄 Routing to tier-specific dashboard:', tierRoute);
-    await navigateTo(tierRoute, { replace: true });
+    navigateTo(tierRoute, { replace: true });
   } else {
-    console.log('🔄 User not authenticated, redirecting to login');
-    await navigateTo('/login');
+    console.warn('❌ No user or tier found - this should not happen after auth middleware');
+    // Fallback - middleware should have caught this
+    navigateTo('/login');
   }
   
   loading.value = false;