fix(client): 设置页兑换入口空 onTap 修复 + 新增我的订单入口(桌面侧栏 Settings 路径)

- settings_page 的「兑换&购买」行 onTap 之前是空占位 → 接上 open(redeem)
- 新增「我的订单」行 → open(orders)
- bump 1.0.68+69

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013nMthbVEmQquxBRKb9Fj8u

client/windows/installer/pangolin.iss

@@ -3,7 +3,7 @@
 ; 前置: 先在 client/ 跑 `flutter build windows`(Release),产物在
 ;       ..\..\build\windows\x64\runner\Release
 #define MyAppName "穿山甲 Pangolin"
-#define MyAppVersion "1.0.67"
+#define MyAppVersion "1.0.68"
 #define MyAppPublisher "Pangolin"
 #define MyAppExeName "pangolin_vpn.exe"
 #define BuildDir "..\..\build\windows\x64\runner\Release"