fix: 修复4个已知BUG — P1 ChatList/P2 错误密码/P3 Copilot崩溃/P3超管entrypoint

P1: ChatList.vue — 添加 conversationStats watch fallback，检测 stats>0
   但 chatList 为空时自动触发 fetchConversations
P2: api.js parseAPIErrorResponse — 处理 error 字段为对象时提取 .message
P3: CopilotContainer.vue — activeAssistant 判空保护
P3: 新建 super_admin.html + vite.config.ts rewrite 规则
    (注：entrypoint 仅含样式，Vue应用代码待补)
防御: NotificationTable.vue — 可选链保护 primary_actor.meta 路径

frontend/app/javascript/dashboard/routes/dashboard/notifications/components/NotificationTable.vue

@@ -108,10 +108,10 @@ export default {
           </td>
           <td class="thumbnail--column">
             <Avatar
-              v-if="notificationItem.primary_actor.meta.assignee"
-              :src="notificationItem.primary_actor.meta.assignee.thumbnail"
+              v-if="notificationItem.primary_actor?.meta?.assignee"
+              :src="notificationItem.primary_actor?.meta?.assignee?.thumbnail || ''"
               :size="28"
-              :name="notificationItem.primary_actor.meta.assignee.name"
+              :name="notificationItem.primary_actor?.meta?.assignee?.name || ''"
               rounded-full
             />
           </td>