Refactor mini program environment configuration and remove deprecated debug features

- Simplified the environment configuration in app.js by removing the debug environment options and related functions.
- Set a default API base URL for production while allowing commented options for local and testing environments.
- Cleaned up settings.js by removing the debug environment label and switching functionality, streamlining the user interface.
- Updated documentation to reflect the removal of debug features and added a summary of synchronization requirements in the planning document.

miniprogram/pages/settings/settings.wxml

@@ -109,15 +109,6 @@
       <text class="tip-text">提示：绑定微信号才能使用提现功能</text>
     </view>
 
-    <!-- 开发专用：切换 API 环境（仅开发版显示） -->
-    <view class="dev-switch-card" wx:if="{{isDevMode}}" bindtap="switchApiEnv">
-      <view class="dev-switch-inner">
-        <text class="dev-switch-icon">🌐</text>
-        <text class="dev-switch-text">切换环境</text>
-        <text class="dev-switch-desc">当前：{{apiEnvLabel}}（点击循环：自动→本地→测试→正式）</text>
-      </view>
-    </view>
-
     <!-- 开发专用：切换账号（仅开发版显示） -->
     <view class="dev-switch-card" wx:if="{{isDevMode}}" bindtap="openSwitchAccountModal">
       <view class="dev-switch-inner">