Implement professional error handling and user feedback system

Major UX Improvements:
- Replace all alert() dialogs with elegant toast notifications
- Add comprehensive loading states for all async operations
- Implement client-side form validation with visual feedback
- Add React Error Boundary for graceful error recovery

Components Added:
- Toast notification system with success/error/warning/info types
- useToast hook for easy notification management
- ErrorBoundary component with development error details
- Form validation with real-time feedback

User Experience:
- Professional toast notifications instead of browser alerts
- Loading indicators prevent double-clicks and show progress
- Immediate validation feedback prevents submission errors
- Graceful error recovery with retry options
- Enhanced accessibility with proper ARIA labels

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

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

components/Toast.tsx

@@ -0,0 +1,115 @@
+'use client';
+
+import { useEffect, useState } from 'react';
+
+export type ToastType = 'success' | 'error' | 'warning' | 'info';
+
+export interface Toast {
+  id: string;
+  type: ToastType;
+  title: string;
+  message?: string;
+  duration?: number;
+}
+
+interface ToastProps {
+  toast: Toast;
+  onRemove: (id: string) => void;
+}
+
+export function ToastComponent({ toast, onRemove }: ToastProps) {
+  const [isVisible, setIsVisible] = useState(false);
+
+  useEffect(() => {
+    // Animate in
+    setTimeout(() => setIsVisible(true), 10);
+
+    // Auto remove after duration
+    const timer = setTimeout(() => {
+      setIsVisible(false);
+      setTimeout(() => onRemove(toast.id), 300);
+    }, toast.duration || 5000);
+
+    return () => clearTimeout(timer);
+  }, [toast.id, toast.duration, onRemove]);
+
+  const getToastStyles = () => {
+    switch (toast.type) {
+      case 'success':
+        return 'bg-green-500/20 border-green-500/40 text-green-300';
+      case 'error':
+        return 'bg-red-500/20 border-red-500/40 text-red-300';
+      case 'warning':
+        return 'bg-yellow-500/20 border-yellow-500/40 text-yellow-300';
+      case 'info':
+        return 'bg-blue-500/20 border-blue-500/40 text-blue-300';
+      default:
+        return 'bg-gray-500/20 border-gray-500/40 text-gray-300';
+    }
+  };
+
+  const getIcon = () => {
+    switch (toast.type) {
+      case 'success':
+        return '✅';
+      case 'error':
+        return '❌';
+      case 'warning':
+        return '⚠️';
+      case 'info':
+        return 'ℹ️';
+      default:
+        return '📢';
+    }
+  };
+
+  return (
+    <div
+      className={`
+        glass p-4 border rounded-lg min-w-80 max-w-md
+        transform transition-all duration-300 ease-out
+        ${isVisible ? 'translate-x-0 opacity-100' : 'translate-x-full opacity-0'}
+        ${getToastStyles()}
+      `}
+    >
+      <div className="flex items-start gap-3">
+        <span className="text-lg flex-shrink-0">{getIcon()}</span>
+        <div className="flex-1 min-w-0">
+          <div className="font-semibold text-sm">{toast.title}</div>
+          {toast.message && (
+            <div className="text-sm opacity-90 mt-1">{toast.message}</div>
+          )}
+        </div>
+        <button
+          onClick={() => {
+            setIsVisible(false);
+            setTimeout(() => onRemove(toast.id), 300);
+          }}
+          className="text-white/60 hover:text-white text-lg leading-none flex-shrink-0"
+          aria-label="Close notification"
+        >
+          ×
+        </button>
+      </div>
+    </div>
+  );
+}
+
+interface ToastContainerProps {
+  toasts: Toast[];
+  onRemove: (id: string) => void;
+}
+
+export function ToastContainer({ toasts, onRemove }: ToastContainerProps) {
+  if (toasts.length === 0) return null;
+
+  return (
+    <div className="fixed top-4 right-4 z-50 space-y-3 pointer-events-none">
+      <div className="space-y-3 pointer-events-auto">
+        {toasts.map((toast) => (
+          <ToastComponent key={toast.id} toast={toast} onRemove={onRemove} />
+        ))}
+      </div>
+    </div>
+  );
+}