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/login/page.tsx

@@ -0,0 +1,81 @@
+'use client'
+import { useState } from 'react'
+import { signIn } from 'next-auth/react'
+import { useRouter } from 'next/navigation'
+import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card'
+import { Button } from '@/components/ui/button'
+import { Input } from '@/components/ui/input'
+import { Label } from '@/components/ui/label'
+
+export default function LoginPage() {
+  const router = useRouter()
+  const [email, setEmail] = useState('')
+  const [password, setPassword] = useState('')
+  const [error, setError] = useState('')
+  const [loading, setLoading] = useState(false)
+
+  async function handleSubmit(e: React.FormEvent) {
+    e.preventDefault()
+    setLoading(true)
+    setError('')
+
+    const result = await signIn('credentials', {
+      email,
+      password,
+      redirect: false,
+    })
+
+    if (result?.error) {
+      setError('Invalid email or password')
+      setLoading(false)
+    } else {
+      router.push('/dashboard')
+    }
+  }
+
+  return (
+    <div className="min-h-screen flex items-center justify-center bg-gray-50">
+      <Card className="w-full max-w-md">
+        <CardHeader className="text-center">
+          <div className="mx-auto mb-4 text-4xl">📡</div>
+          <CardTitle className="text-2xl">NFC Attendance Hub</CardTitle>
+          <CardDescription>Sign in to your admin account</CardDescription>
+        </CardHeader>
+        <CardContent>
+          <form onSubmit={handleSubmit} className="space-y-4">
+            {error && (
+              <div className="bg-red-50 border border-red-200 text-red-700 px-4 py-3 rounded-md text-sm">
+                {error}
+              </div>
+            )}
+            <div className="space-y-2">
+              <Label htmlFor="email">Email</Label>
+              <Input
+                id="email"
+                type="email"
+                value={email}
+                onChange={e => setEmail(e.target.value)}
+                placeholder="admin@example.com"
+                required
+              />
+            </div>
+            <div className="space-y-2">
+              <Label htmlFor="password">Password</Label>
+              <Input
+                id="password"
+                type="password"
+                value={password}
+                onChange={e => setPassword(e.target.value)}
+                placeholder="••••••••"
+                required
+              />
+            </div>
+            <Button type="submit" className="w-full" disabled={loading}>
+              {loading ? 'Signing in...' : 'Sign In'}
+            </Button>
+          </form>
+        </CardContent>
+      </Card>
+    </div>
+  )
+}