refactor: migrate from react-hot-toast to react-toastify and replace all emoji icons with Lucide React

- Replaced react-hot-toast with react-toastify (ToastContainer in providers.tsx)
- Removed @heroicons/react dependency
- Added lucide-react for consistent SVG icon system
- Migrated all 18 frontend pages from emoji icons to Lucide components
- Updated sidebar navigation, login/register, dashboard, apps, deploy,
  tickets, admin users/clusters/pools pages
- All emoji indicators (status, runtime, actions) now use proper SVG icons
- Build passes with zero TypeScript errors

frontend/src/components/providers.tsx

@@ -1,7 +1,8 @@
 'use client';
 
 import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
-import { Toaster } from 'react-hot-toast';
+import { ToastContainer } from 'react-toastify';
+import 'react-toastify/dist/ReactToastify.css';
 import { useEffect, useState } from 'react';
 import { useAuthStore } from '@/lib/store';
 
@@ -28,7 +29,7 @@ export function Providers({ children }: { children: React.ReactNode }) {
   return (
     <QueryClientProvider client={queryClient}>
       {children}
-      <Toaster position="top-right" />
+      <ToastContainer position="top-right" autoClose={3000} hideProgressBar={false} closeOnClick pauseOnHover theme="light" />
     </QueryClientProvider>
   );
 }