Fix React error #130 - Remove authentication race condition

- Remove setTimeout delays in AdminAuthContext login function
- Make authentication state updates synchronous
- Replace setTimeout navigation with state-based navigation in AdminLoginPage
- Add proper error handling and component lifecycle management in CreateEventPage
- Prevent navigation if component unmounts during async operations

This fixes the issue where users would see React error #130 during login
and couldn't create events or save settings.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/pages/admin/CreateEventPage.tsx

@@ -1,4 +1,4 @@
-import React, { useState } from 'react';
+import React, { useState, useRef, useEffect } from 'react';
 import { useNavigate } from 'react-router-dom';
 import { 
   Calendar,
@@ -45,6 +45,13 @@ const COLOR_THEMES = [
 
 export const CreateEventPage: React.FC = () => {
   const navigate = useNavigate();
+  const isMountedRef = useRef(true);
+  
+  useEffect(() => {
+    return () => {
+      isMountedRef.current = false;
+    };
+  }, []);
   
   const [formData, setFormData] = useState<FormData>({
     event_type: 'wedding',
@@ -65,18 +72,27 @@ export const CreateEventPage: React.FC = () => {
   const createMutation = useMutation({
     mutationFn: eventsService.createEvent,
     onSuccess: (data) => {
-      toast.success('Event created successfully!');
-      navigate(`/admin/events/${data.id}`);
+      if (isMountedRef.current) {
+        toast.success('Event created successfully!');
+        navigate(`/admin/events/${data.id}`);
+      }
     },
     onError: (error: any) => {
-      if (error.response?.data?.errors) {
+      if (!isMountedRef.current) return;
+      
+      if (error.code === 'ERR_NETWORK' || error.code === 'ERR_CONNECTION_RESET') {
+        toast.error('Network error. Please check your connection and try again.');
+      } else if (error.response?.data?.errors) {
         const newErrors: Record<string, string> = {};
         error.response.data.errors.forEach((err: any) => {
           newErrors[err.path] = err.msg;
         });
         setErrors(newErrors);
+      } else if (error.response?.status === 401) {
+        toast.error('Session expired. Please login again.');
+        navigate('/admin/login');
       } else {
-        toast.error('Failed to create event');
+        toast.error(error.response?.data?.error || 'Failed to create event');
       }
     },
   });