fix(saas): eliminate 6 compiler warnings + stabilize directive complete

- Remove unused imports: Utc (billing/service), StatusCode (billing/handlers), Sha256 (billing/handlers)
- Fix unused variables: _db (scheduler), _e (payment WeChat error)
- Fix visibility: RegisterDeviceRequest pub(super) → pub (used in pub handler)
- Update STABILIZATION_DIRECTIVE.md: all 7 criteria met, downgrade to advisory
- Fix TRUTH.md §2.2: mark P0/P1 defects as resolved, update Admin pages count to 14

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/zclaw-saas/src/account/handlers.rs

@@ -214,7 +214,7 @@ pub async fn dashboard_stats(
 // ============ Devices ============
 
 #[derive(serde::Deserialize)]
-pub(super) struct RegisterDeviceRequest {
+pub struct RegisterDeviceRequest {
     #[serde(default)]
     device_id: String,
     #[serde(default)]

crates/zclaw-saas/src/billing/handlers.rs

@@ -2,11 +2,9 @@
 
 use axum::{
     extract::{Extension, Form, Path, Query, State},
-    http::StatusCode,
     Json,
 };
 use serde::Deserialize;
-use sha2::Sha256;
 
 use crate::auth::types::AuthContext;
 use crate::error::{SaasError, SaasResult};

crates/zclaw-saas/src/billing/payment.rs

@@ -465,7 +465,7 @@ async fn generate_wechat_url(
     }
 
     let resp_json: serde_json::Value = resp.json().await
-        .map_err(|e| SaasError::Internal("微信支付响应解析失败".into()))?;
+        .map_err(|_| SaasError::Internal("微信支付响应解析失败".into()))?;
 
     let code_url = resp_json.get("code_url")
         .and_then(|v| v.as_str())

crates/zclaw-saas/src/billing/service.rs

@@ -1,6 +1,6 @@
 //! 计费服务层 — 计划查询、订阅管理、用量检查
 
-use chrono::{Datelike, Timelike, Utc};
+use chrono::{Datelike, Timelike};
 
 use sqlx::PgPool;
 

crates/zclaw-saas/src/scheduler.rs

@@ -37,7 +37,7 @@ pub fn parse_duration(s: &str) -> Result<Duration, String> {
 }
 
 /// 启动所有定时任务
-pub fn start_scheduler(config: &SchedulerConfig, db: PgPool, dispatcher: WorkerDispatcher) {
+pub fn start_scheduler(config: &SchedulerConfig, _db: PgPool, dispatcher: WorkerDispatcher) {
     for job in &config.jobs {
         let interval = match parse_duration(&job.interval) {
             Ok(d) => d,