feat(frontend-auth): complete NextAuth.js Keycloak integration with middleware, hooks, and API utility

- Add middleware.ts for route protection (redirects unauthenticated users to /login)
- Add useActiveClub() hook for managing active club context (localStorage + session)
- Add apiClient() fetch wrapper with automatic Authorization + X-Tenant-Id headers
- Configure vitest with jsdom environment and global test setup
- Add comprehensive test coverage: 16/16 tests passing (hooks + API utility)
- Install test dependencies: vitest, @testing-library/react, @vitejs/plugin-react, happy-dom

Task 10 COMPLETE - all acceptance criteria met

frontend/src/hooks/useActiveClub.ts

@@ -0,0 +1,51 @@
+'use client';
+
+import { useSession } from 'next-auth/react';
+import { useState, useEffect } from 'react';
+
+const ACTIVE_CLUB_KEY = 'activeClubId';
+
+export interface ActiveClubData {
+  activeClubId: string | null;
+  role: string | null;
+  clubs: Record<string, string> | null;
+  setActiveClub: (clubId: string) => void;
+}
+
+export function useActiveClub(): ActiveClubData {
+  const { data: session, status } = useSession();
+  const [activeClubId, setActiveClubIdState] = useState<string | null>(null);
+
+  useEffect(() => {
+    if (status === 'authenticated' && session?.user?.clubs) {
+      const clubs = session.user.clubs;
+      const storedClubId = localStorage.getItem(ACTIVE_CLUB_KEY);
+
+      if (storedClubId && clubs[storedClubId]) {
+        setActiveClubIdState(storedClubId);
+      } else {
+        const firstClubId = Object.keys(clubs)[0];
+        if (firstClubId) {
+          setActiveClubIdState(firstClubId);
+        }
+      }
+    }
+  }, [session, status]);
+
+  const setActiveClub = (clubId: string) => {
+    if (session?.user?.clubs && session.user.clubs[clubId]) {
+      localStorage.setItem(ACTIVE_CLUB_KEY, clubId);
+      setActiveClubIdState(clubId);
+    }
+  };
+
+  const clubs = session?.user?.clubs || null;
+  const role = activeClubId && clubs ? clubs[activeClubId] : null;
+
+  return {
+    activeClubId,
+    role,
+    clubs,
+    setActiveClub,
+  };
+}