feat: APP 配置新增企业微信 Schema，写入 Info.plist wxworkSchema 键

与微信登录 AppID 处理一致：填写则写入 Info.plist 的 wxworkSchema，
未配置则移除该键。前端「关联配置」区新增输入框，打包流程透传该字段。

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011wQh7H1Dn3TjQm87TyYgvf

backend/services/build_service.py

@@ -722,7 +722,7 @@ async def generate_config(task_id: str, task, build_dir: Path) -> dict:
 
     # 关联域名等配置
     config_data["ASSOCIATED_DOMAINS"] = app.get("AssDom", "")
-    for key in ["weixinlogin", "weixinpay", "tencent", "UniversalLink", "AlivcLicenseKey"]:
+    for key in ["weixinlogin", "weixinpay", "wxworkSchema", "tencent", "UniversalLink", "AlivcLicenseKey"]:
         if key in app:
             config_data[key] = app[key]