feat: enhance font size toggle functionality in UserPreferencesContext

- Implemented optimistic UI updates for font size changes, cycling through small, medium, and large options.
- Added error handling to revert to original preferences if the server action fails, improving user experience.
- Updated dependencies in the toggleFontSize function to include preferences.viewPreferences for better state management.

src/contexts/UserPreferencesContext.tsx

@@ -130,9 +130,31 @@ export function UserPreferencesProvider({ children, initialPreferences }: UserPr
 
   const toggleFontSize = useCallback(() => {
     startTransition(async () => {
-      await toggleFontSizeAction();
+      const originalPreferences = preferences.viewPreferences;
+      
+      // Optimistic update - cycle through font sizes
+      const fontSizes: ('small' | 'medium' | 'large')[] = ['small', 'medium', 'large'];
+      const currentIndex = fontSizes.indexOf(preferences.viewPreferences.fontSize);
+      const nextIndex = (currentIndex + 1) % fontSizes.length;
+      const newFontSize = fontSizes[nextIndex];
+      
+      setPreferences(prev => ({ 
+        ...prev, 
+        viewPreferences: { ...prev.viewPreferences, fontSize: newFontSize }
+      }));
+      
+      try {
+        const result = await toggleFontSizeAction();
+        if (!result.success) {
+          console.error('Erreur server action:', result.error);
+          setPreferences(prev => ({ ...prev, viewPreferences: originalPreferences }));
+        }
+      } catch (error) {
+        console.error('Erreur lors du toggle de la taille de police:', error);
+        setPreferences(prev => ({ ...prev, viewPreferences: originalPreferences }));
+      }
     });
-  }, []);
+  }, [preferences.viewPreferences]);
 
   // === COLUMN VISIBILITY ===