feat: initial NFC Attendance Hub implementation

- Multi-tenant client management with unique API keys
- Semaphore SMS integration (per-client key + sender name + credit balance)
- DB-based SMS queue with 3-attempt retry and exponential backoff
- Failed SMS dashboard with manual retry button
- Reports page with date/client filter and CSV export
- Admin auth via NextAuth (email/password)
- Docker Compose setup (app + PostgreSQL 16)
- Prisma 5 schema with SmsQueue, SmsLog, Client, User models

Tech: Next.js 14 App Router + TypeScript + Tailwind CSS + Prisma + PostgreSQL

app/dashboard/clients/page.tsx

@@ -0,0 +1,86 @@
+import Link from 'next/link'
+import { prisma } from '@/lib/prisma'
+import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
+import { Button } from '@/components/ui/button'
+import { Badge } from '@/components/ui/badge'
+import { Plus, Settings } from 'lucide-react'
+
+export default async function ClientsPage() {
+  const clients = await prisma.client.findMany({
+    orderBy: { createdAt: 'desc' },
+    include: {
+      _count: { select: { smsQueue: true, smsLogs: true } },
+    },
+  })
+
+  return (
+    <div className="space-y-6">
+      <div className="flex items-center justify-between">
+        <div>
+          <h1 className="text-3xl font-bold text-gray-900">Clients</h1>
+          <p className="text-gray-500 mt-1">Manage schools and organizations</p>
+        </div>
+        <Link href="/dashboard/clients/new">
+          <Button>
+            <Plus className="h-4 w-4 mr-2" />
+            Add Client
+          </Button>
+        </Link>
+      </div>
+
+      {clients.length === 0 ? (
+        <Card>
+          <CardContent className="text-center py-16">
+            <p className="text-gray-500 mb-4">No clients yet</p>
+            <Link href="/dashboard/clients/new">
+              <Button>
+                <Plus className="h-4 w-4 mr-2" />
+                Add Your First Client
+              </Button>
+            </Link>
+          </CardContent>
+        </Card>
+      ) : (
+        <div className="grid gap-4">
+          {clients.map(client => (
+            <Card key={client.id}>
+              <CardContent className="p-6">
+                <div className="flex items-center justify-between">
+                  <div className="flex-1">
+                    <div className="flex items-center gap-3">
+                      <h3 className="font-semibold text-lg">{client.name}</h3>
+                      <Badge variant={client.isActive ? 'success' : 'secondary'}>
+                        {client.isActive ? 'Active' : 'Inactive'}
+                      </Badge>
+                      {client.semaphoreKey ? (
+                        <Badge variant="outline" className="text-xs">SMS Configured</Badge>
+                      ) : (
+                        <Badge variant="warning" className="text-xs">⚠ No SMS Key</Badge>
+                      )}
+                    </div>
+                    <div className="mt-2 space-y-1">
+                      <p className="text-sm text-gray-500">
+                        <span className="font-medium">API Key:</span>{' '}
+                        <code className="bg-gray-100 px-2 py-0.5 rounded text-xs">{client.apiKey}</code>
+                      </p>
+                      <p className="text-sm text-gray-500">
+                        <span className="font-medium">Sender:</span> {client.senderName || 'NFC-HUB'} ·{' '}
+                        <span className="font-medium">SMS sent:</span> {client._count.smsLogs}
+                      </p>
+                    </div>
+                  </div>
+                  <Link href={`/dashboard/clients/${client.id}`}>
+                    <Button variant="outline" size="sm">
+                      <Settings className="h-4 w-4 mr-2" />
+                      Settings
+                    </Button>
+                  </Link>
+                </div>
+              </CardContent>
+            </Card>
+          ))}
+        </div>
+      )}
+    </div>
+  )
+}