fix(calendar-lab): enable hover on grid cells by removing pointer-events block

Content overlay layer was intercepting mouse events (pointer-events: auto
with z-index: 5), preventing :hover from reaching the grid cells underneath.
Removed pointer-events: auto from .canvas-content-visible since the content
layer is purely visual and needs no click handling.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/app/components/workspace/calendar/lab/CrmCalendarZoomCanvasLab.vue

@@ -820,6 +820,6 @@ onBeforeUnmount(() => {
 }
 
 .canvas-content-visible {
-  pointer-events: auto;
+  /* pointer-events stay none — grid cells underneath must receive hover */
 }
 </style>