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/industry/service.rs

@@ -15,24 +15,48 @@ pub async fn list_industries(
 ) -> SaasResult<PaginatedResponse<IndustryListItem>> {
     let (page, page_size, offset) = normalize_pagination(query.page, query.page_size);
 
-    // 动态构建参数化查询 — 所有用户输入通过 $N 绑定
-    let mut where_parts: Vec<String> = vec!["1=1".to_string()];
-    let mut param_idx = 3; // $1=LIMIT, $2=OFFSET, $3+=filters
     let status_param: Option<String> = query.status.clone();
     let source_param: Option<String> = query.source.clone();
 
+    // 构建 WHERE 条件 — 每个查询独立的参数编号
+    let mut where_parts: Vec<String> = vec!["1=1".to_string()];
+
+    // count 查询：参数从 $1 开始
+    let mut count_params: Vec<String> = Vec::new();
+    let mut count_idx = 1;
     if status_param.is_some() {
-        where_parts.push(format!("status = ${}", param_idx));
-        param_idx += 1;
+        count_params.push(format!("status = ${}", count_idx));
+        count_idx += 1;
     }
     if source_param.is_some() {
-        where_parts.push(format!("source = ${}", param_idx));
-        param_idx += 1;
+        count_params.push(format!("source = ${}", count_idx));
+        count_idx += 1;
     }
-    let where_sql = where_parts.join(" AND ");
+    let count_where = if count_params.is_empty() {
+        "1=1".to_string()
+    } else {
+        format!("1=1 AND {}", count_params.join(" AND "))
+    };
+
+    // items 查询：$1=LIMIT, $2=OFFSET, $3+=filters
+    let mut items_params: Vec<String> = Vec::new();
+    let mut items_idx = 3;
+    if status_param.is_some() {
+        items_params.push(format!("status = ${}", items_idx));
+        items_idx += 1;
+    }
+    if source_param.is_some() {
+        items_params.push(format!("source = ${}", items_idx));
+        items_idx += 1;
+    }
+    let items_where = if items_params.is_empty() {
+        "1=1".to_string()
+    } else {
+        format!("1=1 AND {}", items_params.join(" AND "))
+    };
 
     // count 查询
-    let count_sql = format!("SELECT COUNT(*) FROM industries WHERE {}", where_sql);
+    let count_sql = format!("SELECT COUNT(*) FROM industries WHERE {}", count_where);
     let mut count_q = sqlx::query_scalar::<_, i64>(&count_sql);
     if let Some(ref s) = status_param { count_q = count_q.bind(s); }
     if let Some(ref s) = source_param { count_q = count_q.bind(s); }
@@ -44,7 +68,7 @@ pub async fn list_industries(
          COALESCE(jsonb_array_length(keywords), 0) as keywords_count, \
          created_at, updated_at \
          FROM industries WHERE {} ORDER BY source, id LIMIT $1 OFFSET $2",
-        where_sql
+        items_where
     );
     let mut items_q = sqlx::query_as::<_, IndustryListItem>(&items_sql)
         .bind(page_size as i64)