feat(task-list-v2): enhance sticky column behavior and dark mode support

- Updated DropSpacer and EmptyGroupMessage components to accept an optional isDarkMode prop for improved styling in dark mode.
- Enhanced task rendering in TaskRow to dynamically adjust background colors based on dark mode and drag states.
- Refactored useTaskRowColumns to support sticky column positioning and hover effects, ensuring a consistent user experience across different themes.
- Improved overall visual feedback during task interactions, including drag-and-drop operations.

worklenz-frontend/src/components/task-list-v2/TaskRow.tsx

@@ -131,11 +131,26 @@ const TaskRow: React.FC<TaskRowProps> = memo(({
         isOver && !isDragging ? 'bg-blue-50 dark:bg-blue-900/20' : ''
       }`}
     >
-      {visibleColumns.map((column, index) => (
-        <React.Fragment key={column.id}>
-          {renderColumn(column.id, column.width, column.isSticky, index)}
-        </React.Fragment>
-      ))}
+      {visibleColumns.map((column, index) => {
+        // Calculate background state for sticky columns - custom dark mode colors
+        const rowBackgrounds = {
+          normal: isDarkMode ? '#1e1e1e' : '#ffffff', // custom dark : bg-white
+          hover: isDarkMode ? '#1f2937' : '#f9fafb', // slightly lighter dark : bg-gray-50  
+          dragOver: isDarkMode ? '#1e3a8a33' : '#dbeafe', // bg-blue-900/20 : bg-blue-50
+        };
+        
+        let currentBg = rowBackgrounds.normal;
+        if (isOver && !isDragging) {
+          currentBg = rowBackgrounds.dragOver;
+        }
+        // Note: hover state is handled by CSS, so we'll use a CSS custom property
+        
+        return (
+          <React.Fragment key={column.id}>
+            {renderColumn(column.id, column.width, column.isSticky, index, currentBg, rowBackgrounds)}
+          </React.Fragment>
+        );
+      })}
     </div>
   );
 });