feat(routes): implement lazy loading and suspense fallback for route components

- Refactored account setup, admin center, reporting, and settings routes to utilize React's lazy loading for improved performance.
- Wrapped route components in Suspense with a fallback UI to enhance user experience during loading states.
- Removed unused drag-and-drop CSS file to clean up the codebase.

worklenz-frontend/src/components/task-management/drag-drop-optimized.css

@@ -1,40 +0,0 @@
-/* MINIMAL DRAG AND DROP CSS - SHOW ONLY TASK NAME */
-
-/* Basic drag handle styling */
-.drag-handle-optimized {
-  cursor: grab;
-  opacity: 0.6;
-  transition: opacity 0.2s ease;
-}
-
-.drag-handle-optimized:hover {
-  opacity: 1;
-}
-
-.drag-handle-optimized:active {
-  cursor: grabbing;
-}
-
-/* Simple drag overlay - just show task name */
-[data-dnd-overlay] {
-  background: white;
-  border: 1px solid #d9d9d9;
-  border-radius: 4px;
-  padding: 8px 12px;
-  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
-  pointer-events: none;
-  z-index: 9999;
-}
-
-/* Dark mode support for drag overlay */
-.dark [data-dnd-overlay],
-[data-theme="dark"] [data-dnd-overlay] {
-  background: #1f1f1f;
-  border-color: #404040;
-  color: white;
-}
-
-/* Hide drag handle during drag */
-[data-dnd-dragging="true"] .drag-handle-optimized {
-  opacity: 0;
-}