Improves all-day event hover detection

Enhances the all-day event selection by creating transparent, full-height columns for each day, which enables more accurate and reliable hover detection across all-day events.

Now selects all-day events by hovering on the entire column, not just day headers.

wwwroot/css/calendar-layout-css.css

@@ -288,11 +288,23 @@ swp-allday-container {
   overflow: hidden;
 }
 
+/* Ghost columns for mouseenter events */
+swp-allday-column {
+  position: relative;
+  opacity: 0; /* Invisible but functional */
+  pointer-events: auto; /* Enable mouse events */
+  background: transparent;
+  z-index: 1; /* Below all-day events */
+  height: 100%;
+}
+
 /* All-day events in containers */
 swp-allday-event {
   height: 22px; /* Fixed height for consistent stacking */
   background: #ff9800; /* Default orange background */
   display: flex;
+  position: relative;
+  z-index: 2; /* Above ghost columns */
   align-items: center;
   justify-content: flex-start;
   color: #fff;