feat: implement complex selection flow

apps/frontend/src/routes/auth-callback.tsx

@@ -0,0 +1,50 @@
+import { useEffect } from 'react';
+import { apiClient } from '@/lib/api-client';
+import { useAuth } from '@/lib/auth';
+import { createFileRoute, useNavigate } from '@tanstack/react-router';
+
+function AuthCallbackPage() {
+  const navigate = useNavigate();
+  const { isAuthenticated } = useAuth();
+
+  useEffect(() => {
+    async function handleCallback() {
+      if (!isAuthenticated) {
+        navigate({ to: '/login' });
+        return;
+      }
+
+      try {
+        const complexes = await apiClient.complexes.listMine();
+
+        if (complexes.length === 1) {
+          await apiClient.complexes.select({ complexId: complexes[0].id });
+          navigate({ to: '/' });
+        } else if (complexes.length > 1) {
+          const current = await apiClient.complexes.getCurrent();
+          if (current) {
+            navigate({ to: '/' });
+          } else {
+            navigate({ to: '/select-complex' });
+          }
+        } else {
+          navigate({ to: '/' });
+        }
+      } catch {
+        navigate({ to: '/login' });
+      }
+    }
+
+    handleCallback();
+  }, [isAuthenticated, navigate]);
+
+  return (
+    <main className="flex min-h-screen w-full items-center justify-center px-6">
+      <p className="text-sm text-muted-foreground">Completando sesión...</p>
+    </main>
+  );
+}
+
+export const Route = createFileRoute('/auth-callback')({
+  component: AuthCallbackPage,
+});