refactor(mp): 统一空状态为 EmptyState 组件 + 清理旧 Tab CSS

- 4 个页面的内联空状态替换为共享 EmptyState 组件
  (messages / action-inbox / pkg-health/alerts / mall)
- 清理 10 个页面的旧 Tab CSS（迁移到 SegmentTabs 后不再需要）
- 清理 elder-mode 中已删除的 mall-empty-state 引用

apps/miniprogram/src/pages/messages/index.scss

@@ -86,19 +86,6 @@
   gap: 8px;
 }
 
-.msg-empty {
-  background: $card;
-  border-radius: $r;
-  padding: 48px 24px;
-  text-align: center;
-  box-shadow: $shadow-sm;
-}
-
-.msg-empty-text {
-  font-size: var(--tk-font-cap);
-  color: $tx2;
-}
-
 /* ─── 咨询卡片 ─── */
 .consult-card {
   display: flex;

apps/miniprogram/src/pages/messages/index.tsx

@@ -5,6 +5,7 @@ import { listConsultations, ConsultationSession } from '../../services/consultat
 import { notificationService } from '../../services/notification';
 import Loading from '../../components/Loading';
 import ErrorState from '../../components/ErrorState';
+import EmptyState from '../../components/EmptyState';
 import GuestGuard from '../../components/GuestGuard';
 import { useAuthStore } from '../../stores/auth';
 import { useElderClass } from '../../hooks/useElderClass';
@@ -152,9 +153,7 @@ export default function Messages() {
           loading ? (
             <Loading />
           ) : sessions.length === 0 ? (
-            <View className='msg-empty'>
-              <Text className='msg-empty-text'>暂无咨询消息</Text>
-            </View>
+            <EmptyState text='暂无咨询消息' />
           ) : (
             <View className='msg-list'>
               {sessions.map((session) => {
@@ -201,9 +200,7 @@ export default function Messages() {
           loading ? (
             <Loading />
           ) : notifications.length === 0 ? (
-            <View className='msg-empty'>
-              <Text className='msg-empty-text'>暂无新通知</Text>
-            </View>
+            <EmptyState text='暂无新通知' />
           ) : (
             <View className='msg-list'>
               {notifications.map((n) => {