fix(saas): admin_guard_middleware — 非 admin 用户统一返回 403

BUG-M4 修复: 之前非 admin 用户发送 malformed body 到 admin 端点时，
Axum 先反序列化 body 返回 422，绕过了权限检查。

- 新增 admin_guard_middleware (auth/mod.rs) 在中间件层拦截
- account::admin_routes() 拆分 (dashboard 独立)
- billing::admin_routes() + account::admin_routes() 加 guard layer
- 非 admin 用户无论 body 是否合法，统一返回 403

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

@@ -16,8 +16,13 @@ pub fn routes() -> axum::Router<crate::state::AppState> {
         .route("/api/v1/tokens", post(handlers::create_token))
         .route("/api/v1/tokens/:id", delete(handlers::revoke_token))
         .route("/api/v1/logs/operations", get(handlers::list_operation_logs))
-        .route("/api/v1/admin/dashboard", get(handlers::dashboard_stats))
         .route("/api/v1/devices", get(handlers::list_devices))
         .route("/api/v1/devices/register", post(handlers::register_device))
         .route("/api/v1/devices/heartbeat", post(handlers::device_heartbeat))
 }
+
+/// Admin-only 路由 (需 admin_guard_middleware 保护)
+pub fn admin_routes() -> axum::Router<crate::state::AppState> {
+    axum::Router::new()
+        .route("/api/v1/admin/dashboard", get(handlers::dashboard_stats))
+}

crates/zclaw-saas/src/auth/mod.rs

@@ -203,6 +203,27 @@ pub async fn auth_middleware(
     }
 }
 
+/// Admin 路由守卫中间件: 确保 AuthContext 具有 admin/super_admin 角色
+/// 必须在 auth_middleware 之后使用（依赖 Extension<AuthContext>）
+pub async fn admin_guard_middleware(
+    mut req: Request,
+    next: Next,
+) -> Response {
+    use crate::auth::handlers::check_permission;
+
+    let ctx = req.extensions().get::<AuthContext>().cloned();
+    match ctx {
+        Some(ctx) => {
+            if let Err(e) = check_permission(&ctx, "account:admin") {
+                e.into_response()
+            } else {
+                next.run(req).await
+            }
+        }
+        None => SaasError::Unauthorized.into_response(),
+    }
+}
+
 /// 路由 (无需认证的端点)
 pub fn routes() -> axum::Router<AppState> {
     use axum::routing::post;

crates/zclaw-saas/src/main.rs

@@ -352,6 +352,10 @@ async fn build_router(state: AppState) -> axum::Router {
 
     let protected_routes = zclaw_saas::auth::protected_routes()
         .merge(zclaw_saas::account::routes())
+        .merge(
+            zclaw_saas::account::admin_routes()
+                .layer(middleware::from_fn(zclaw_saas::auth::admin_guard_middleware))
+        )
         .merge(zclaw_saas::model_config::routes())
         // relay::routes() 不在此合并 — SSE 端点需要更长超时，在最终 Router 单独合并
         .merge(zclaw_saas::migration::routes())
@@ -361,7 +365,10 @@ async fn build_router(state: AppState) -> axum::Router {
         .merge(zclaw_saas::scheduled_task::routes())
         .merge(zclaw_saas::telemetry::routes())
         .merge(zclaw_saas::billing::routes())
-        .merge(zclaw_saas::billing::admin_routes())
+        .merge(
+            zclaw_saas::billing::admin_routes()
+                .layer(middleware::from_fn(zclaw_saas::auth::admin_guard_middleware))
+        )
         .merge(zclaw_saas::knowledge::routes())
         .merge(zclaw_saas::industry::routes())
         .layer(middleware::from_fn_with_state(