feat(voice): 语音参数移入 config.js + 设置页男女声切换

- config: 新增 tts.female/male 两组参数(voiceType/volume/speed),
  直接改数字即可调音色,无需改逻辑代码
- storage: getSettings 兜底 voiceGender(旧用户迁移为女声)
- voice: 新增 _getTtsParams 读 config+性别;缓存 key 含完整参数,
  改音色/音量/性别自动重新合成,无需手动清缓存
- settings: 训练偏好加"语音音色"segmented(女声/男声)
- tts 云函数: _synthesize 用传入 opts 合成;_upload 路径含 voiceType
  (男/女不同文件);需重新部署

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

pages/settings/settings.wxml

@@ -118,6 +118,21 @@
       </view>
       <switch checked="{{voiceGuide}}" bindchange="onToggleVoice" color="{{theme.primary}}"/>
     </view>
+    <view class="setting-row">
+      <view class="setting-left">
+        <image class="setting-icon" src="{{icons.voiceFill}}" mode="aspectFit"></image>
+        <text class="setting-label">语音音色</text>
+      </view>
+      <view class="segmented">
+        <view
+          class="segmented-item {{voiceGender === item.key ? 'active' : ''}}"
+          wx:for="{{voiceGenderOptions}}"
+          wx:key="key"
+          data-key="{{item.key}}"
+          bindtap="onSelectVoiceGender"
+        >{{item.name}}</view>
+      </view>
+    </view>
     <view class="setting-row">
       <view class="setting-left">
         <image class="setting-icon" src="{{icons.notificationFill}}" mode="aspectFit"></image>