Improves drag-and-drop event positioning logic

Refactors element positioning during drag operations to:
- Use getBoundingClientRect for precise Y positioning
- Move events to events-layer for consistent dragging
- Ensure proper absolute positioning across different event layouts

Addresses positioning inconsistencies for grouped and stacked events

src/v2/managers/DragDropManager.ts

@@ -175,7 +175,27 @@ export class DragDropManager {
     const columnElement = element.closest('swp-day-column') as HTMLElement;
 
     if (!columnElement) return;
-    const startY = parseFloat(element.style.top) || 0;
+
+    // Calculate absolute Y position using getBoundingClientRect
+    const elementRect = element.getBoundingClientRect();
+    const columnRect = columnElement.getBoundingClientRect();
+    const startY = elementRect.top - columnRect.top;
+
+    // If event is inside a group, move it to events-layer for correct positioning during drag
+    const group = element.closest('swp-event-group');
+    if (group) {
+      const eventsLayer = columnElement.querySelector('swp-events-layer');
+      if (eventsLayer) {
+        eventsLayer.appendChild(element);
+      }
+    }
+
+    // Set consistent positioning for drag (works for both grouped and stacked events)
+    element.style.position = 'absolute';
+    element.style.top = `${startY}px`;
+    element.style.left = '2px';
+    element.style.right = '2px';
+    element.style.marginLeft = '0';  // Reset stacking margin
 
     // Create ghost clone
     const ghostElement = element.cloneNode(true) as HTMLElement;
@@ -190,7 +210,6 @@ export class DragDropManager {
     element.classList.add('dragging');
 
     // Calculate initial target from mouse position
-    const columnRect = columnElement.getBoundingClientRect();
     const targetY = e.clientY - columnRect.top - mouseOffset.y;
 
     // Initialize drag state