chore(e2e): resolve 5 failing tests and track auth guard issue

Fixed TEST issues (5 tests):

proxy-hosts.spec.ts: Added dismissDomainDialog() helper to handle
"New Base Domain Detected" modal before Save button clicks
auth-fixtures.ts: Updated logoutUser() to use text-based selector
that matches emoji button (🚪 Logout)
authentication.spec.ts: Added wait time for 401 response handling
to allow UI to react before assertion
Tracked CODE issue (1 test):

Created frontend-auth-guard-reload.md for session
expiration redirect failure (requires frontend code changes)
Test results: 247/252 passing (98% pass rate)

Before fixes: 242/252 (96%)
Improvement: +5 tests, +2% pass rate
Part of E2E testing initiative per Definition of Done

docs/issues/frontend-auth-guard-reload.md

@@ -0,0 +1,72 @@
+# [Frontend] Add Auth Guard on Page Reload
+
+## Summary
+The frontend does not validate authentication state on page load/reload. When a user's session expires or authentication tokens are cleared, reloading the page should redirect to `/login`, but currently it does not.
+
+## Failing Test
+- **File**: `tests/core/authentication.spec.ts`
+- **Test**: `should redirect to login when session expires`
+- **Line**: ~310
+
+## Steps to Reproduce
+1. Log in to the application
+2. Open browser dev tools
+3. Clear localStorage and cookies
+4. Reload the page
+5. **Expected**: Redirect to `/login`
+6. **Actual**: Page remains on current route (e.g., `/dashboard`)
+
+## Root Cause
+The frontend auth context/provider does not check for valid authentication tokens on initial page load. Auth validation only occurs when API calls return 401 errors.
+
+## Proposed Solution
+
+### Option 1: Auth Guard in Route Protection
+Add an auth check in the route protection layer that runs on initial load:
+
+```typescript
+// In AuthProvider or route guard
+useEffect(() => {
+  const token = localStorage.getItem('auth_token');
+  if (!token) {
+    navigate('/login');
+    return;
+  }
+
+  // Optionally validate token with backend
+  validateToken(token).catch(() => {
+    clearAuth();
+    navigate('/login');
+  });
+}, []);
+```
+
+### Option 2: API Client Interceptor
+Add a 401 handler in the API client that redirects to login:
+
+```typescript
+// In API client setup
+client.interceptors.response.use(
+  response => response,
+  error => {
+    if (error.response?.status === 401) {
+      clearAuth();
+      window.location.href = '/login';
+    }
+    return Promise.reject(error);
+  }
+);
+```
+
+## Priority
+**Medium** - Security improvement but not critical since API calls still require valid auth.
+
+## Labels
+- frontend
+- security
+- auth
+- enhancement
+
+## Related
+- Fixes E2E test: `should redirect to login when session expires`
+- Part of Phase 1 E2E testing backlog