feat: enhance CMS editor with rich text features and fix line break preservation

- Fix line break preservation with proper HardBreak extension configuration
- Add text alignment support (left, center, right, justify) for paragraphs and headings
- Add H4-H6 heading support with keyboard shortcuts
- Add code block support with syntax highlighting for multiple languages
- Enhance preview functionality with split-pane view (Edit/Preview/Split modes)
- Add custom prose CSS overrides for proper content rendering
- Update DOMPurify configuration to preserve br tags and text alignment
- Add visual indicators and help modal with all keyboard shortcuts
- Improve toolbar organization with grouped buttons and separators
- Add auto-save status indicator and word/character count

Fixes issues with:
- Line breaks not showing in gallery view
- Limited heading options (only H1-H3)
- No text formatting capabilities
- Missing preview functionality

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

Co-Authored-By: Claude <[email protected]>

frontend/src/pages/public/LegalPage.tsx

@@ -7,6 +7,7 @@ import DOMPurify from 'dompurify';
 import { Loading, Card } from '../../components/common';
 import { cmsService } from '../../services/cms.service';
 import { api } from '../../config/api';
+import '../../styles/prose-overrides.css';
 
 export const LegalPage: React.FC = () => {
   const { slug } = useParams<{ slug: string }>();
@@ -104,7 +105,20 @@ export const LegalPage: React.FC = () => {
             
             <div 
               className="prose prose-neutral max-w-none"
-              dangerouslySetInnerHTML={{ __html: DOMPurify.sanitize(page.content) }}
+              dangerouslySetInnerHTML={{ 
+                __html: DOMPurify.sanitize(page.content, {
+                  ALLOWED_TAGS: [
+                    'p', 'br', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6',
+                    'ul', 'ol', 'li', 'blockquote', 'a', 'em', 'strong',
+                    'code', 'pre', 'hr', 'div', 'span'
+                  ],
+                  ALLOWED_ATTR: ['href', 'target', 'rel', 'class', 'style'],
+                  ALLOW_DATA_ATTR: false,
+                  KEEP_CONTENT: true,
+                  ADD_TAGS: ['br'], // Explicitly allow br tags
+                  ADD_ATTR: ['style'], // Allow style for text alignment
+                })
+              }}
             />
             
           </Card>