fix: Update design of the conversation sidebar, chatlist (#10572)

- Increase the sidebar and chatlist width on screens bigger than 2xl
- Fix background of the copilot sidebar
- Increase the breakpoint for hiding chatlist from 1024 to 1200

app/javascript/dashboard/components/widgets/conversation/ConversationSidebar.vue

@@ -51,7 +51,7 @@ const showCopilotTab = computed(() => {
 
 <template>
   <div
-    class="ltr:border-l rtl:border-r border-n-weak h-full overflow-hidden z-10 min-w-[300px] w-[300px] flex flex-col bg-n-solid-2"
+    class="ltr:border-l rtl:border-r border-n-weak h-full overflow-hidden z-10 min-w-[300px] w-[300px] 2xl:min-w-96 2xl:w-96 flex flex-col bg-n-background"
   >
     <div v-if="showCopilotTab" class="p-2">
       <TabBar