fix(admin): 行业选择500修复 + 管理员切换订阅计划

- fix(industry): list_industries SQL参数编号错位 — count查询和items查询
  共用WHERE子句但参数从$3开始，sqlx bind按$1/$2顺序绑定导致500
- feat(billing): 新增 PUT /admin/accounts/:id/subscription 端点 (super_admin)
  验证目标计划 → 取消当前订阅 → 创建新订阅(30天) → 同步配额
- feat(admin-v2): Accounts.tsx 编辑弹窗新增「订阅计划」选择区
  显示所有活跃计划，保存时调用admin switch plan API

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

@@ -7,6 +7,7 @@ use axum::{
 use serde::Deserialize;
 
 use crate::auth::types::AuthContext;
+use crate::auth::handlers::{log_operation, check_permission};
 use crate::error::{SaasError, SaasResult};
 use crate::state::AppState;
 use super::service;
@@ -115,6 +116,41 @@ pub async fn increment_usage_dimension(
     })))
 }
 
+/// POST /api/v1/billing/payments — 创建支付订单
+
+/// PUT /api/v1/admin/accounts/:id/subscription — 管理员切换用户订阅计划（仅 super_admin）
+pub async fn admin_switch_subscription(
+    State(state): State<AppState>,
+    Extension(ctx): Extension<AuthContext>,
+    Path(account_id): Path<String>,
+    Json(req): Json<AdminSwitchPlanRequest>,
+) -> SaasResult<Json<serde_json::Value>> {
+    // 仅 super_admin 可操作
+    check_permission(&ctx, "admin:full")?;
+
+    // 验证 plan_id 非空
+    if req.plan_id.trim().is_empty() {
+        return Err(SaasError::InvalidInput("plan_id 不能为空".into()));
+    }
+
+    let sub = service::admin_switch_plan(&state.db, &account_id, &req.plan_id).await?;
+
+    log_operation(
+        &state.db,
+        &ctx.account_id,
+        "billing.admin_switch_plan",
+        "account",
+        &account_id,
+        Some(serde_json::json!({ "plan_id": req.plan_id })),
+        None,
+    ).await.ok(); // 日志失败不影响主流程
+
+    Ok(Json(serde_json::json!({
+        "success": true,
+        "subscription": sub,
+    })))
+}
+
 /// POST /api/v1/billing/payments — 创建支付订单
 pub async fn create_payment(
     State(state): State<AppState>,