Adds dynamic header hiding for date groupings

Introduces hideHeader option for date grouping configurations
Enables suppressing date headers in specific views like day view
Improves calendar view flexibility by conditionally rendering headers

wwwroot/css/v2/calendar-v2-layout.css

@@ -68,6 +68,48 @@ swp-view-switcher {
   &:focus { outline: 2px solid var(--color-primary); outline-offset: 1px; }
 }
 
+/* Resource selector (picker view) */
+swp-resource-selector {
+  &.hidden { display: none; }
+
+  fieldset {
+    border: 1px solid var(--color-border);
+    border-radius: 6px;
+    padding: 6px 12px;
+    margin: 0;
+  }
+
+  legend {
+    font-size: 11px;
+    font-weight: 500;
+    color: var(--color-text-secondary);
+    padding: 0 6px;
+  }
+
+  .resource-checkboxes {
+    display: flex;
+    flex-wrap: wrap;
+    gap: 4px 16px;
+  }
+
+  label {
+    display: flex;
+    align-items: center;
+    gap: 4px;
+    font-size: 12px;
+    cursor: pointer;
+    white-space: nowrap;
+
+    &:hover { color: var(--color-primary); }
+  }
+
+  input[type="checkbox"] {
+    width: 14px;
+    height: 14px;
+    cursor: pointer;
+  }
+}
+
 /* Navigation group */
 swp-nav-group {
   display: flex;
@@ -289,6 +331,10 @@ swp-day-header {
     font-size: 24px;
     font-weight: 300;
   }
+
+  &[data-hidden="true"] {
+    display: none;
+  }
 }
 
 /* Scrollable content */