Refactors event rendering and display

Improves event rendering by introducing dedicated event
renderers and streamlining event display logic.

- Adds a base event renderer and specialized date and
  resource-based renderers to handle event display logic.
- Renders all-day events within a dedicated container in the
  calendar header.
- Removes the direct filtering of all-day events from the
  `GridManager`.
- Fixes an issue where the 'Summer Festival' event started on the
  wrong date.

The changes enhance the flexibility and maintainability of the
calendar, provide dedicated containers and styling for allday events and fix date issues related to certain events

wwwroot/css/calendar-layout-css.css

@@ -266,10 +266,20 @@ swp-day-header[data-today="true"] swp-day-date {
 }
 
 
-/* All-day events in row 2 */
+/* All-day event container - spans columns as needed */
+swp-allday-container {
+  display: grid;
+  grid-template-columns: 1fr; /* Single column for now, can expand later */
+  grid-auto-rows: min-content;
+  gap: 2px;
+  padding: 2px;
+  height: 100%;
+  overflow: hidden;
+}
+
+/* All-day events in containers */
 swp-allday-event {
-  grid-row: 2; /* Row 2 only */
-  height: calc(var(--all-day-row-height) - 3px); /* Dynamic height minus margin */
+  height: 22px; /* Fixed height for consistent stacking */
   background: #ff9800; /* Default orange background */
   display: flex;
   align-items: center;
@@ -277,16 +287,15 @@ swp-allday-event {
   color: #fff;
   font-size: 0.75rem;
   padding: 2px 4px;
-  margin: 1px;
   border-radius: 3px;
   overflow: hidden;
   text-overflow: ellipsis;
   white-space: nowrap;
-  border-right: 1px solid rgba(0, 0, 0, 0.1);
+  border-left: 3px solid rgba(0, 0, 0, 0.2);
 }
 
 swp-allday-event:last-child {
-  border-right: none; /* Remove border from last all-day event */
+  margin-bottom: 0;
 }
 
 /* Scrollable content */