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/ai/advisor.go

@@ -0,0 +1,24 @@
+package ai
+
+type Mode string
+
+const (
+	ModeOff     Mode = "off"
+	ModeSuggest Mode = "suggest"
+	ModeExplain Mode = "explain"
+)
+
+type Advisor interface {
+	Suggest(userInput string) (string, error)
+	Explain(result string) (string, error)
+}
+
+type NoopAdvisor struct{}
+
+func (NoopAdvisor) Suggest(userInput string) (string, error) {
+	return "", nil
+}
+
+func (NoopAdvisor) Explain(result string) (string, error) {
+	return "", nil
+}