fix: 工单提交422错误处理 + SQL模板占位符校验

- TicketCreatePage: Pydantic 422 detail 是对象数组，前端错误处理改为检测数组并拼接 msg
- QueriesPage: 执行前检查 SQL 中未替换的 {table}/{db}/{collection} 占位符，阻止执行
- QueriesPage: 同步修复 422 detail 数组的错误处理

frontend/src/pages/TicketCreatePage.tsx

@@ -398,8 +398,10 @@ export default function TicketCreatePage() {
       });
       navigate('/tickets');
     } catch (e: unknown) {
-      const err = e as { response?: { data?: { detail?: string } } };
-      setError(err?.response?.data?.detail || '提交失败，请稍后重试');
+      const err = e as { response?: { data?: { detail?: string | Array<{ msg: string }> } } };
+      const raw = err?.response?.data?.detail;
+      const msg = Array.isArray(raw) ? raw.map((v) => v.msg).join('; ') : (raw || '提交失败，请稍后重试');
+      setError(msg);
     } finally { setSubmitting(false); }
   }, [title, sqlContent, instanceId, database, reason, priority, rollbackSql, instances, dbType, navigate]);