fix(test): replace vi.mocked with type casting for Bun compatibility

Fixes technical debt from Tasks 10, 18-20.

Problem:
- 38/46 frontend tests failing due to vi.mocked() not supported in Bun
- happy-dom environment causing document errors in some tests

Solution:
1. Replaced all vi.mocked(fn) calls with (fn as any) type casting
   - useActiveClub.test.ts: 3 occurrences (localStorage mocks)
   - auth-guard.test.tsx: 13 occurrences (useSession, useTenant, useRouter)
   - club-switcher.test.tsx: 3 occurrences (useRouter)
   - task-detail.test.tsx: 4 occurrences (useRouter, useTasks)
   - task-list.test.tsx: 1 occurrence (useTasks)

2. Updated vitest.config.ts:
   - Changed environment from happy-dom to jsdom (better DOM support)
   - Added exclude pattern to prevent e2e tests interference

Test Results:
- Before: 8/46 passing (38 failures)
- After: 45/45 passing (0 failures) ✅

No source code changes - only test infrastructure fixes.

frontend/src/hooks/__tests__/useActiveClub.test.ts

@@ -33,15 +33,15 @@ describe('useActiveClub', () => {
       status: 'authenticated',
     });
     
-    vi.mocked(localStorage.getItem).mockImplementation((key: string) => {
+    (localStorage.getItem as any).mockImplementation((key: string) => {
       return localStorageData[key] || null;
     });
     
-    vi.mocked(localStorage.setItem).mockImplementation((key: string, value: string) => {
+    (localStorage.setItem as any).mockImplementation((key: string, value: string) => {
       localStorageData[key] = value;
     });
     
-    vi.mocked(localStorage.clear).mockImplementation(() => {
+    (localStorage.clear as any).mockImplementation(() => {
       localStorageData = {};
     });
   });