feat(frontend): implement step 11 — pages, components, and routing with React Query

frontend/src/pages/LoginPage.tsx

@@ -1,11 +1,52 @@
+import { useState } from 'react'
+import { useNavigate } from 'react-router-dom'
+import { login } from '../api/authApi'
+
 export default function LoginPage() {
+  const [password, setPassword] = useState('')
+  const [error, setError] = useState<string | null>(null)
+  const navigate = useNavigate()
+
+  const handleSubmit = async (e: React.FormEvent) => {
+    e.preventDefault()
+    setError(null)
+    try {
+      await login({ password })
+      navigate('/', { replace: true })
+    } catch {
+      setError('Invalid password')
+    }
+  }
+
   return (
     <div className="flex min-h-screen items-center justify-center bg-gray-50">
       <div className="w-full max-w-sm rounded-lg bg-white p-8 shadow">
         <h1 className="mb-6 text-2xl font-bold text-gray-900">
           Condado Abaixo da Média SA
         </h1>
-        <p className="text-sm text-gray-500">Login page — coming in Step 11.</p>
+        <form onSubmit={handleSubmit} className="space-y-4">
+          <div>
+            <label htmlFor="password" className="block text-sm font-medium text-gray-700">
+              Password
+            </label>
+            <input
+              id="password"
+              type="password"
+              value={password}
+              onChange={(e) => setPassword(e.target.value)}
+              className="mt-1 block w-full rounded border border-gray-300 px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-blue-500"
+            />
+          </div>
+          {error && (
+            <p className="text-sm text-red-600">{error}</p>
+          )}
+          <button
+            type="submit"
+            className="w-full rounded bg-blue-600 px-4 py-2 text-sm font-medium text-white hover:bg-blue-700"
+          >
+            Login
+          </button>
+        </form>
       </div>
     </div>
   )