fix(frontend): Fix auth hydration and auto-redirect to login

Fix issue where unauthenticated users were not automatically
redirected to the login page.

Root Cause:
- authStore.ts: isLoading was not set to false after hydration
- AuthGuard.tsx: Used isLoading instead of isHydrated for checks

Changes:
- Set isLoading = false in authStore onRehydrateStorage callback
- Changed AuthGuard to use isHydrated instead of isLoading
- Added console log for redirect debugging

This ensures:
- Hydration completes with correct loading state
- Unauthenticated users are immediately redirected to /login
- More explicit state management with isHydrated

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

stores/authStore.ts

@@ -57,9 +57,11 @@ export const useAuthStore = create<AuthState>()(
           }
 
           state.isHydrated = true;
+          state.isLoading = false; // 水合完成后停止 loading
           console.log('[AuthStore] Hydration completed', {
             userId: state.user?.id,
-            isAuthenticated: state.isAuthenticated
+            isAuthenticated: state.isAuthenticated,
+            isLoading: state.isLoading
           });
         }
       },