style(chat): make jump calendar popover background fully opaque

src/components/JumpToDatePopover.scss

@@ -5,7 +5,7 @@
   width: 312px;
   border-radius: 14px;
   border: 1px solid var(--border-color);
-  background: var(--bg-secondary);
+  background: var(--bg-secondary-solid, #ffffff);
   opacity: 1;
   backdrop-filter: none;
   -webkit-backdrop-filter: none;
@@ -32,7 +32,7 @@
   height: 28px;
   border: 1px solid var(--border-color);
   border-radius: 8px;
-  background: var(--bg-secondary);
+  background: var(--bg-secondary-solid, #ffffff);
   color: var(--text-secondary);
   display: inline-flex;
   align-items: center;