feat(mobile): redesign today home and switch mentor persona to female

- today: immersive community hero + hold-to-talk voice card, numbered
  schedule rows, common-functions grid (learning/report/question-board)
- login: female mentor bust; sop: female mentor chat avatars
- speech: raise browser-fallback mentor pitch to match female voice

mobile-uni/src/pages/user/sop/index.vue

@@ -17,7 +17,7 @@
     <scroll-view scroll-y class="chat-thread" :scroll-top="threadScrollTop" :scroll-with-animation="true">
       <view class="thread-inner">
         <view class="bubble-row left">
-          <view class="avatar master-avatar">师</view>
+          <image class="avatar master-avatar" src="/static/mentor-female-avatar.png" mode="aspectFill" />
           <view class="bubble master">
             <text class="bubble-text">你好，我是老师傅。工作里的 SOP、话术、流程直接问我，答案都带引用依据；也可以按住下面的按钮说话。</text>
           </view>
@@ -37,14 +37,14 @@
           </view>
 
           <view v-else-if="msg.role === 'pending'" class="bubble-row left">
-            <view class="avatar master-avatar">师</view>
+            <image class="avatar master-avatar" src="/static/mentor-female-avatar.png" mode="aspectFill" />
             <view class="bubble master pending-bubble">
               <text class="bubble-text">师傅思考中…</text>
             </view>
           </view>
 
           <view v-else class="bubble-row left">
-            <view class="avatar master-avatar">师</view>
+            <image class="avatar master-avatar" src="/static/mentor-female-avatar.png" mode="aspectFill" />
             <view class="master-col">
               <view v-if="msg.voiceStatus !== 'unavailable'" class="voice-line">
                 <view
@@ -154,7 +154,7 @@
         </template>
 
         <view v-if="!loggedIn" class="bubble-row left">
-          <view class="avatar master-avatar">师</view>
+          <image class="avatar master-avatar" src="/static/mentor-female-avatar.png" mode="aspectFill" />
           <view class="bubble master">
             <text class="bubble-text">登录后才能查询 SOP、生成总结卡并反馈答案。</text>
             <view class="bubble-actions">
@@ -2066,7 +2066,8 @@ onUnload(() => {
 }
 
 .master-avatar {
-  background: #e70014;
+  overflow: hidden;
+  background: #f3f4f6;
   color: #ffffff;
 }