chore: address clawpatch review findings (test scope, deps, legal-page hardening)

- frontend: `npm test` now runs all 7 vitest suites instead of one hardcoded
  file; the previously skipped ProtectedImage / Skeleton / usePublicSettings /
  contrast / themeMigration / url suites are now active in CI
- frontend: wrap ThemeCustomizerEnhanced test in QueryClientProvider so the
  newly-enabled run passes (component uses useQuery internally)
- root: drop unused better-sqlite3 / canvas / node-fetch + their
  prebuild-install/tar-fs override (backend keeps its own copies); add dotenv
  so playwright.config.ts can load on a clean install; add name/version/private
- LegalPage: scheme-validate external_url before window.location.replace so a
  CMS edit can't redirect visitors to javascript:/data:
- LegalPage: force rel="noopener noreferrer" on target="_blank" anchors in
  sanitized CMS HTML to block reverse-tabnabbing

frontend/src/components/admin/__tests__/ThemeCustomizerEnhanced.test.tsx

@@ -1,6 +1,8 @@
 import { render, screen } from '@testing-library/react';
 import userEvent from '@testing-library/user-event';
 import { vi } from 'vitest';
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
+import type { ReactElement } from 'react';
 
 import { ThemeCustomizerEnhanced } from '../ThemeCustomizerEnhanced';
 import type { ThemeConfig } from '../../../types/theme.types';
@@ -15,6 +17,16 @@ vi.mock('react-i18next', async () => {
   };
 });
 
+// Component uses useQuery for admin-settings + fonts; tests don't exercise
+// those data paths, so just give them a client that won't retry on the
+// (intentionally absent) network.
+const renderWithQueryClient = (ui: ReactElement) => {
+  const queryClient = new QueryClient({
+    defaultOptions: { queries: { retry: false } }
+  });
+  return render(<QueryClientProvider client={queryClient}>{ui}</QueryClientProvider>);
+};
+
 describe('ThemeCustomizerEnhanced', () => {
   const baseTheme: ThemeConfig = {
     primaryColor: '#000000',
@@ -32,7 +44,7 @@ describe('ThemeCustomizerEnhanced', () => {
     const handleChange = vi.fn();
     const handleApply = vi.fn().mockResolvedValue(undefined);
 
-    render(
+    renderWithQueryClient(
       <ThemeCustomizerEnhanced
         value={baseTheme}
         onChange={handleChange}
@@ -55,7 +67,7 @@ describe('ThemeCustomizerEnhanced', () => {
   it('disables the Apply button while applying', () => {
     const handleChange = vi.fn();
 
-    render(
+    renderWithQueryClient(
       <ThemeCustomizerEnhanced
         value={baseTheme}
         onChange={handleChange}

frontend/src/pages/public/LegalPage.tsx

@@ -9,6 +9,30 @@ import { cmsService } from '../../services/cms.service';
 import { usePublicSettings } from '../../hooks/usePublicSettings';
 import '../../styles/prose-overrides.css';
 
+// Force rel="noopener noreferrer" on target="_blank" anchors in CMS-authored
+// HTML so editors can't accidentally (or maliciously) introduce reverse
+// tabnabbing via the legal pages.
+DOMPurify.addHook('afterSanitizeAttributes', (node) => {
+  if (node.tagName === 'A' && node.getAttribute('target') === '_blank') {
+    node.setAttribute('rel', 'noopener noreferrer');
+  }
+});
+
+// CMS-configured external_url may be edited by lower-privileged staff; reject
+// anything outside http(s) so the legal route can't be turned into a
+// javascript:/data: launcher.
+const sanitizeExternalUrl = (url: string): string | null => {
+  try {
+    const parsed = new URL(url, window.location.origin);
+    if (parsed.protocol !== 'https:' && parsed.protocol !== 'http:') {
+      return null;
+    }
+    return parsed.toString();
+  } catch {
+    return null;
+  }
+};
+
 export const LegalPage: React.FC = () => {
   const { slug } = useParams<{ slug: string }>();
   const { i18n } = useTranslation();
@@ -47,12 +71,15 @@ export const LegalPage: React.FC = () => {
   // External-URL override: full-page redirect so the visitor lands on the
   // operator's own canonical legal page. Use replace() so the back button
   // returns to the gallery instead of looping back through the redirect.
-  const willRedirect = !!(page?.use_external_url && page?.external_url);
+  const safeExternalUrl = page?.use_external_url && page?.external_url
+    ? sanitizeExternalUrl(page.external_url)
+    : null;
+  const willRedirect = !!safeExternalUrl;
   useEffect(() => {
-    if (willRedirect && page?.external_url) {
-      window.location.replace(page.external_url);
+    if (safeExternalUrl) {
+      window.location.replace(safeExternalUrl);
     }
-  }, [willRedirect, page?.external_url]);
+  }, [safeExternalUrl]);
 
   if (isLoading || willRedirect) {
     return (