style(ai): align chat drawer top bars to a single 48px row

The conversation-list sidebar header and the chat panel header lived
in separate columns with different heights — the "+ New conversation"
wrapper was ~60px (p-3 + py-2 button) while the "AI Assistant" header
was ~44px (p-3 + small icon/text). The resulting staircase looked
unintentional.

Pins both to h-12 (48px) so they form a single unified top bar across
the drawer. Shrinks the "+ New conversation" button to text-xs /
py-1 / px-2 so it fits the tighter height without clipping, and
switches its alignment to center to match the compacter footprint.

resources/scripts/features/company/ai/components/AiChatConversationList.vue

@@ -17,10 +17,10 @@ async function remove(convo: AiConversationSummary, event: MouseEvent): Promise<
 
 <template>
   <div class="flex flex-col h-full">
-    <div class="p-3 border-b border-line-default">
+    <div class="h-12 px-3 border-b border-line-default flex items-center">
       <button
         type="button"
-        class="w-full text-left text-sm font-medium rounded px-3 py-2 bg-btn-primary text-white hover:bg-btn-primary-hover"
+        class="w-full text-center text-xs font-medium rounded px-2 py-1 bg-btn-primary text-white hover:bg-btn-primary-hover"
         @click="store.newConversation()"
       >
         + {{ $t('ai.chat.new_conversation') }}

resources/scripts/features/company/ai/components/AiChatDrawer.vue

@@ -58,7 +58,7 @@ async function onSend(message: string): Promise<void> {
 
         <!-- Messages + input -->
         <div class="flex-1 flex flex-col">
-          <div class="flex items-center justify-between p-3 border-b border-line-default">
+          <div class="h-12 flex items-center justify-between px-3 border-b border-line-default">
             <div class="flex items-center gap-2">
               <BaseIcon name="SparklesIcon" class="w-5 h-5 text-primary-500" />
               <h2 class="text-sm font-semibold text-heading">