style: 优化通知弹窗滚动区域高度样式

将DiplomaticNotifications、EnemyAlertNotifications与QueueNotifications中的ScrollArea高度由固定h-96/h-[420px]调整为h-auto max-h-96，提升内容自适应性，避免内容较少时出现多余空白，增强界面美观与一致性。

src/components/notifications/DiplomaticNotifications.vue

@@ -19,7 +19,7 @@
           {{ t('diplomacy.markAllRead') }}
         </Button>
       </div>
-      <ScrollArea class="h-96">
+      <ScrollArea class="h-auto max-h-96">
         <Empty v-if="allNotifications.length === 0" class="border-0">
           <EmptyContent>
             <ScrollText class="h-10 w-10 text-muted-foreground" />

src/components/notifications/EnemyAlertNotifications.vue

@@ -19,7 +19,7 @@
           {{ t('enemyAlert.markAllRead') }}
         </Button>
       </div>
-      <ScrollArea class="h-96">
+      <ScrollArea class="h-auto max-h-96">
         <Empty v-if="activeAlerts.length === 0" class="border-0">
           <EmptyContent>
             <Shield class="h-10 w-10 text-muted-foreground" />

src/components/notifications/QueueNotifications.vue

@@ -32,7 +32,7 @@
           </TabsTrigger>
         </TabsList>
 
-        <ScrollArea class="h-[420px]">
+        <ScrollArea class="h-auto max-h-96">
           <TabsContent v-for="tab in tabConfig" :key="tab.value" :value="tab.value" class="mt-0">
             <Empty v-if="tab.items.length === 0" class="border-0">
               <EmptyContent>