fix(ui): portal menus to body above the sidedocks

src/tailwind.css

@@ -109,6 +109,17 @@
   background: var(--background);
 }
 
+/* Portal layer for menus: a zero-sized anchor at body level, above the sidedocks. */
+.bcal-portal {
+  position: fixed;
+  top: 0;
+  left: 0;
+  width: 0;
+  height: 0;
+  background: transparent;
+  z-index: var(--layer-menu, 65);
+}
+
 .bcal-app {
   container-type: inline-size;
   display: flex;