feat: add LoginCallback page and route for OAuth redirect handling

packages/web/src/App.tsx

@@ -5,6 +5,7 @@ import { ThemeProvider } from './lib/theme';
 import { I18nProvider } from './lib/i18n';
 import Login from './pages/Login';
 import Register from './pages/Register';
+import LoginCallback from './pages/LoginCallback';
 import Layout from './pages/Layout';
 import Projects from './pages/Projects';
 import ProjectDetail from './pages/ProjectDetail';
@@ -22,6 +23,7 @@ export default function App() {
                 <Route path="/" element={<LandingPage />} />
                 <Route path="/login" element={<Login />} />
                 <Route path="/register" element={<Register />} />
+                <Route path="/login/callback" element={<LoginCallback />} />
                 <Route path="/dashboard" element={<Layout />}>
                   <Route index element={<Projects />} />
                   <Route path="projects/:id" element={<ProjectDetail />} />

packages/web/src/pages/LoginCallback.tsx

@@ -0,0 +1,67 @@
+import { useEffect, useState } from 'react';
+import { useNavigate, useSearchParams, Link } from 'react-router-dom';
+import { useAuth } from '../lib/auth';
+import { useI18n } from '../lib/i18n';
+
+export default function LoginCallback() {
+  const [searchParams] = useSearchParams();
+  const [error, setError] = useState('');
+  const { loginWithTokens } = useAuth();
+  const navigate = useNavigate();
+  const { t } = useI18n();
+
+  useEffect(() => {
+    const accessToken = searchParams.get('accessToken');
+    const refreshToken = searchParams.get('refreshToken');
+    const errorParam = searchParams.get('error');
+
+    if (errorParam) {
+      setError(errorParam);
+      return;
+    }
+
+    if (!accessToken || !refreshToken) {
+      setError('Missing authentication tokens');
+      return;
+    }
+
+    // Clear tokens from URL immediately
+    window.history.replaceState({}, '', '/login/callback');
+
+    loginWithTokens(accessToken, refreshToken)
+      .then(() => navigate('/dashboard', { replace: true }))
+      .catch((err) => setError(err instanceof Error ? err.message : 'Authentication failed'));
+  }, []);
+
+  if (error) {
+    return (
+      <div className="min-h-screen flex items-center justify-center bg-bg-primary">
+        <div className="text-center max-w-sm mx-4">
+          <div className="w-12 h-12 rounded-full bg-danger-muted mx-auto flex items-center justify-center mb-4">
+            <svg className="w-6 h-6 text-danger" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
+              <circle cx="12" cy="12" r="10" />
+              <path d="M15 9l-6 6m0-6l6 6" />
+            </svg>
+          </div>
+          <h1 className="text-lg font-semibold text-text-primary mb-2">{t('auth.callback.error')}</h1>
+          <p className="text-[13px] text-text-muted mb-6">{error}</p>
+          <Link to="/login" className="btn-primary inline-block px-6">
+            {t('auth.callback.retry')}
+          </Link>
+        </div>
+      </div>
+    );
+  }
+
+  return (
+    <div className="min-h-screen flex items-center justify-center bg-bg-primary">
+      <div className="text-center">
+        <svg className="w-8 h-8 animate-spin text-accent mx-auto mb-4" fill="none" viewBox="0 0 24 24">
+          <circle className="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" strokeWidth="4" />
+          <path className="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4z" />
+        </svg>
+        <p className="text-[13px] text-text-muted">{t('auth.callback.loading')}</p>
+      </div>
+    </div>
+  );
+}