fix: preserve URL hash and OIDC redirect target through login flow

- Include location.hash in redirect param at all three producer sites
  (ProtectedRoute, axios 401 interceptor, OAuthAuthorizePage) so
  hash fragments survive the login bounce
- Stash redirectTarget in sessionStorage before any OIDC provider
  redirect and restore it after the code exchange, since the IdP
  strips the original ?redirect= param during the roundtrip
- Clear sessionStorage on OIDC error to avoid stale state
- Add tests covering sessionStorage stash on mount, navigate to saved
  redirect after OIDC exchange, fallback to /dashboard, and cleanup
  on error

client/src/App.tsx

@@ -58,7 +58,7 @@ function ProtectedRoute({ children, adminRequired = false, addonId }: ProtectedR
   }
 
   if (!isAuthenticated) {
-    const redirectParam = encodeURIComponent(location.pathname + location.search)
+    const redirectParam = encodeURIComponent(location.pathname + location.search + location.hash)
     return <Navigate to={`/login?redirect=${redirectParam}`} replace />
   }
 

client/src/api/client.ts

@@ -75,7 +75,7 @@ apiClient.interceptors.response.use(
     if (error.response?.status === 401 && (error.response?.data as { code?: string } | undefined)?.code === 'AUTH_REQUIRED') {
       const { pathname } = window.location
       if (!isAuthPublicPath(pathname)) {
-        const currentPath = pathname + window.location.search
+        const currentPath = pathname + window.location.search + window.location.hash
         window.location.href = '/login?redirect=' + encodeURIComponent(currentPath)
       }
     }

client/src/pages/LoginPage.oidc-redirect.test.tsx

@@ -0,0 +1,105 @@
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
+import { render, screen, waitFor } from '../../tests/helpers/render';
+import { http, HttpResponse } from 'msw';
+import { server } from '../../tests/helpers/msw/server';
+import { resetAllStores } from '../../tests/helpers/store';
+import LoginPage from './LoginPage';
+
+const mockNavigate = vi.fn();
+vi.mock('react-router-dom', async () => {
+  const actual = await vi.importActual('react-router-dom');
+  return { ...actual, useNavigate: () => mockNavigate };
+});
+
+describe('LoginPage — OIDC redirect preservation', () => {
+  let savedLocation: Location;
+
+  beforeEach(() => {
+    resetAllStores();
+    mockNavigate.mockClear();
+    sessionStorage.clear();
+    savedLocation = window.location;
+  });
+
+  afterEach(() => {
+    Object.defineProperty(window, 'location', {
+      configurable: true,
+      writable: true,
+      value: savedLocation,
+    });
+  });
+
+  function setSearch(search: string) {
+    Object.defineProperty(window, 'location', {
+      configurable: true,
+      writable: true,
+      value: { ...window.location, search },
+    });
+  }
+
+  describe('FE-PAGE-LOGIN-022: redirect param stashed in sessionStorage on mount', () => {
+    it('saves decoded redirect to sessionStorage when ?redirect= is present', async () => {
+      setSearch('?redirect=%2Foauth%2Fauthorize%3Fclient_id%3Dfoo');
+      render(<LoginPage />);
+
+      await waitFor(() => {
+        expect(sessionStorage.getItem('oidc_redirect')).toBe('/oauth/authorize?client_id=foo');
+      });
+    });
+
+    it('does not write to sessionStorage when no redirect param is present', async () => {
+      render(<LoginPage />);
+      await waitFor(() => {
+        expect(screen.getByPlaceholderText('your@email.com')).toBeInTheDocument();
+      });
+
+      expect(sessionStorage.getItem('oidc_redirect')).toBeNull();
+    });
+  });
+
+  describe('FE-PAGE-LOGIN-023: OIDC code exchange navigates to sessionStorage redirect', () => {
+    beforeEach(() => {
+      server.use(
+        http.get('/api/auth/oidc/exchange', () =>
+          HttpResponse.json({ token: 'mock-oidc-token' })
+        ),
+      );
+    });
+
+    it('navigates to the saved sessionStorage redirect after successful OIDC exchange', async () => {
+      sessionStorage.setItem('oidc_redirect', '/oauth/authorize?client_id=foo&state=xyz');
+      setSearch('?oidc_code=testcode123');
+      render(<LoginPage />);
+
+      await waitFor(() => {
+        expect(mockNavigate).toHaveBeenCalledWith(
+          '/oauth/authorize?client_id=foo&state=xyz',
+          { replace: true },
+        );
+      });
+
+      expect(sessionStorage.getItem('oidc_redirect')).toBeNull();
+    });
+
+    it('falls back to /dashboard when no sessionStorage redirect is set', async () => {
+      setSearch('?oidc_code=testcode123');
+      render(<LoginPage />);
+
+      await waitFor(() => {
+        expect(mockNavigate).toHaveBeenCalledWith('/dashboard', { replace: true });
+      });
+    });
+  });
+
+  describe('FE-PAGE-LOGIN-024: OIDC error clears sessionStorage redirect', () => {
+    it('removes oidc_redirect from sessionStorage on OIDC error', async () => {
+      sessionStorage.setItem('oidc_redirect', '/oauth/authorize?client_id=foo');
+      setSearch('?oidc_error=token_failed');
+      render(<LoginPage />);
+
+      await waitFor(() => {
+        expect(sessionStorage.getItem('oidc_redirect')).toBeNull();
+      });
+    });
+  });
+});

client/src/pages/LoginPage.tsx

@@ -55,6 +55,12 @@ export default function LoginPage(): React.ReactElement {
     return '/dashboard'
   }, [])
 
+  useEffect(() => {
+    if (redirectTarget !== '/dashboard') {
+      sessionStorage.setItem('oidc_redirect', redirectTarget)
+    }
+  }, [redirectTarget])
+
   useEffect(() => {
     const params = new URLSearchParams(window.location.search)
 
@@ -83,7 +89,9 @@ export default function LoginPage(): React.ReactElement {
           window.history.replaceState({}, '', '/login')
           if (data.token) {
             await loadUser()
-            navigate('/dashboard', { replace: true })
+            const savedRedirect = sessionStorage.getItem('oidc_redirect') || '/dashboard'
+            sessionStorage.removeItem('oidc_redirect')
+            navigate(savedRedirect, { replace: true })
           } else {
             setError(data.error || t('login.oidcFailed'))
           }
@@ -104,6 +112,7 @@ export default function LoginPage(): React.ReactElement {
         invalid_state: t('login.oidc.invalidState'),
       }
       setError(errorMessages[oidcError] || oidcError)
+      sessionStorage.removeItem('oidc_redirect')
       window.history.replaceState({}, '', '/login')
       return
     }

client/src/pages/OAuthAuthorizePage.tsx

@@ -124,7 +124,7 @@ export default function OAuthAuthorizePage(): React.ReactElement {
   }
 
   function handleLoginRedirect() {
-    const next = '/oauth/authorize?' + params.toString()
+    const next = '/oauth/authorize?' + params.toString() + window.location.hash
     window.location.href = '/login?redirect=' + encodeURIComponent(next)
   }