fix: i18n system overhaul and sidebar UI bugs

- Fix LanguageProvider: add RTL support (ar/fa), translation caching,
  prevent blank flash during load, browser language detection
- Fix detect-user-language: extend whitelist from 5 to all 15 languages
- Remove hardcoded initialLanguage="fr" from auth layout
- Complete fr.json translation (all sections translated from English)
- Add missing admin.ai keys to all 13 non-English locales
- Translate ai.autoLabels, ai.batchOrganization, memoryEcho sections
  for all locales
- Remove duplicate top-level autoLabels/batchOrganization from en.json
- Fix notebook creation: replace window.location.reload() with
  createNotebookOptimistic + router.refresh()
- Fix notebook name truncation in sidebar with min-w-0
- Remove redundant router.refresh() after note creation in page.tsx

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

keep-notes/components/masonry-grid.tsx

@@ -26,7 +26,7 @@ interface MasonryItemProps {
   isDragging?: boolean;
 }
 
-const MasonryItem = function MasonryItem({ note, onEdit, onResize, onNoteSizeChange, onDragStart, onDragEnd, isDragging }: MasonryItemProps) {
+const MasonryItem = memo(function MasonryItem({ note, onEdit, onResize, onNoteSizeChange, onDragStart, onDragEnd, isDragging }: MasonryItemProps) {
   const resizeRef = useResizeObserver(onResize);
 
   useEffect(() => {
@@ -55,7 +55,7 @@ const MasonryItem = function MasonryItem({ note, onEdit, onResize, onNoteSizeCha
       </div>
     </div>
   );
-};
+})
 
 export function MasonryGrid({ notes, onEdit }: MasonryGridProps) {
   const { t } = useLanguage();