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/app/dashboard/admin/clusters/page.tsx

@@ -3,8 +3,9 @@
 import { useState } from 'react';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import api from '@/lib/api';
-import toast from 'react-hot-toast';
+import { toast } from 'react-toastify';
 import type { Cluster, ClusterResources } from '@/types';
+import { Server, CheckCircle, XCircle, BarChart3, Clock, RotateCw, Plug, X } from 'lucide-react';
 
 function ResourcePanel({ clusterId }: { clusterId: string }) {
   const { data, isLoading, error } = useQuery<ClusterResources>({
@@ -201,7 +202,7 @@ export default function AdminClustersPage() {
           <p className="page-subtitle">{clusters.length} cluster{clusters.length !== 1 ? 's' : ''} registered</p>
         </div>
         <button onClick={() => setShowForm(!showForm)} className={showForm ? 'btn-ghost' : 'btn-primary'}>
-          {showForm ? '✕ Cancel' : '+ Add Cluster'}
+          {showForm ? <><X className="w-4 h-4 inline" /> Cancel</> : '+ Add Cluster'}
         </button>
       </div>
 
@@ -263,7 +264,7 @@ export default function AdminClustersPage() {
             disabled={!form.name || !form.apiServer || !form.kubeconfig || createMutation.isPending}
             className="btn-primary"
           >
-            {createMutation.isPending ? '🔄 Verifying connection & adding...' : 'Add Cluster'}
+            {createMutation.isPending ? <><RotateCw className="w-4 h-4 inline animate-spin" /> Verifying connection & adding...</> : 'Add Cluster'}
           </button>
         </div>
       )}
@@ -283,7 +284,7 @@ export default function AdminClustersPage() {
         </div>
       ) : clusters.length === 0 ? (
         <div className="card text-center py-16">
-          <div className="text-5xl mb-4">🖥️</div>
+          <Server className="w-12 h-12 mx-auto text-gray-300 mb-4" />
           <p className="text-gray-600 font-medium">No clusters registered yet.</p>
           <p className="text-gray-400 text-sm mt-1">Add a Kubernetes cluster to start deploying applications.</p>
         </div>
@@ -296,7 +297,7 @@ export default function AdminClustersPage() {
                   <div className={`w-11 h-11 rounded-xl flex items-center justify-center shrink-0 ${
                     cluster.status === 'active' ? 'bg-emerald-50' : 'bg-red-50'
                   }`}>
-                    {cluster.status === 'active' ? '✅' : '❌'}
+                    {cluster.status === 'active' ? <CheckCircle className="w-5 h-5 text-emerald-500" /> : <XCircle className="w-5 h-5 text-red-500" />}
                   </div>
                   <div className="min-w-0">
                     <div className="flex items-center gap-2 flex-wrap">
@@ -322,14 +323,14 @@ export default function AdminClustersPage() {
                     onClick={() => toggleResources(cluster.id)}
                     className={`btn-ghost text-sm ${expandedResources.has(cluster.id) ? 'bg-purple-50 text-purple-700' : ''}`}
                   >
-                    📊 Resources
+                    <BarChart3 className="w-4 h-4 inline" /> Resources
                   </button>
                   <button
                     onClick={() => testMutation.mutate(cluster.id)}
                     disabled={testingId === cluster.id}
                     className="btn-ghost text-sm disabled:opacity-50"
                   >
-                    {testingId === cluster.id ? '⏳ Testing...' : '🔌 Test'}
+                    {testingId === cluster.id ? <><Clock className="w-3 h-3 inline animate-spin" /> Testing...</> : <><Plug className="w-3 h-3 inline" /> Test</>}
                   </button>
                   <button
                     onClick={() => { if (confirm('Remove this cluster?')) deleteMutation.mutate(cluster.id); }}