feat: comprehensive CMS improvements

- Fix DOMPurify SSR crash (use isomorphic-dompurify)
- Fix SanitizedHtml to sanitize by default
- Add auth guards to studio/catalog maintenance pages
- Add update/edit to vouchers CRUD
- Add update/edit to rare-values CRUD
- Add approve workflow to applications page
- Add edit form to guilds detail page
- Add SEO metadata to all public pages (21 pages)
- Fix mobile nav accessibility (focus trap, aria attributes)
- Fix missing labels and table accessibility
- Add dynamic imports for heavy client components (6 components)
- Fix silent error swallowing (40+ locations)
- Add content scheduling for articles (publishAt, status)
- Wire up 12 missing webhook notification triggers
- Add global search to admin panel
- Add bulk actions to admin users table
- Fix JSON formatting and a11y issues

.gitignore

@@ -33,3 +33,4 @@ public/tmp/
 
 # Test coverage reports
 coverage/
+.aider*