feat: 模块化命令框架 + runbook 严格断言与查询结果回传

- core/module: 命令模板、门控（feature flag/confirm/dry-run）、ecode 错误标签、ResultFormatter
- runbook executor: http.get/http.post/assert.json(expect_success 严格断言)、目标主机管理、任务落库、最终 stdout 直接回传
- cf 模块: /cf dns list 支持域名自动解析 zone_id；dns list/zones/workers list 格式化回传；API success:false 判真失败
- 全部 CF/CPA runbook 接入严格断言，杜绝假阳性 success
- 新增 cpa/cfdav/mail/sub 模块与 runbooks；QQ 订阅到期提醒调度
- Web 后台: 模块设置(CF/CPA/cfdav/AI)、OPS 任务、渠道管理、审计页

internal/core/ecode/codes.go

@@ -0,0 +1,17 @@
+package ecode
+
+const (
+	ErrPermissionDenied = "ERR_PERMISSION_DENIED"
+	ErrConfirmRequired  = "ERR_CONFIRM_REQUIRED"
+	ErrFeatureDisabled  = "ERR_FEATURE_DISABLED"
+	ErrStepFailed       = "ERR_STEP_FAILED"
+	ErrJobCancelled     = "ERR_JOB_CANCELLED"
+	ErrStepTimeout      = "ERR_STEP_TIMEOUT"
+)
+
+func Tag(code, msg string) string {
+	if code == "" {
+		return msg
+	}
+	return "[" + code + "] " + msg
+}