feat(debug): temporary BLE debug page for on-device verification

- entry in profile menu, visible only while a device is connected
- live FFE4 readout: 7x PD, VBAT, fitting, scan wave marker, run state
- tap a face-map region to fire a 2s single-region treat command
  (verifies region-to-IO mapping on the physical mask)
- wavelength selector (red/ir/uv/yellow) to verify color byte order
- scan command / full-face 2s / stop buttons, hex log of every write
- intentionally not i18n'd; remove page before release

miniprogram/pages/profile/profile.wxml

@@ -50,6 +50,12 @@
         <view class="menu-text">{{i18n.profile.menuHistory}}</view>
         <text class="menu-arrow">›</text>
       </view>
+      <!-- 临时调试入口：仅设备已连接时显示，上线前移除 -->
+      <view class="menu-item" wx:if="{{debugVisible}}" bindtap="onOpenDebug">
+        <view class="menu-icon">🔧</view>
+        <view class="menu-text">调试工具（临时）</view>
+        <text class="menu-arrow">›</text>
+      </view>
       <view class="menu-item" bindtap="onViewSubscription" wx:if="{{!subscription || subscription.plan !== 'free'}}">
         <view class="menu-icon">💳</view>
         <view class="menu-text">{{i18n.profile.menuSubscription}}</view>