fix(calendar(css)): enlarge categories color stripes

Fixes #5301

UI/WebServerResources/scss/core/structure.scss

@@ -38,7 +38,7 @@ html * {
   top: 0;
   bottom: 0;
   width: 10%;
-  z-index: $z-index-view;
+  z-index: -1;
 }
 
 // Group fields of a form

UI/WebServerResources/scss/views/SchedulerUI.scss

@@ -164,12 +164,13 @@ $quarter_height: 10px;
           border-bottom-right-radius: $block_radius;
         }
       }
+
+      .eventInside .text {
+        position: static;
+        padding: 3px 1%;
+      }
     }
 
-    .text {
-      position: static;
-      padding: 3px 1%;
-    }
   }
 
   // Toolbar of all-day events when expanded to display all events