fix(settings): 实时监控设置页左右两列等宽 (#102)

grid-cols-[1fr_1fr] 的 1fr 等价于 minmax(auto,1fr),左列较长内容
撑出最小宽度挤压右列;改用 minmax(0,1fr) 强制严格等分。

Co-authored-by: shy3130 <shy3130@users.noreply.github.com>

frontend/src/pages/settings/Monitoring.tsx

@@ -284,7 +284,7 @@ export function SettingsMonitoringPanel({ highlight }: { highlight?: string } =
   }
 
   return (
-    <div className="grid grid-cols-1 lg:grid-cols-[1fr_1fr] gap-6 max-w-5xl">
+    <div className="grid grid-cols-1 lg:grid-cols-[minmax(0,1fr)_minmax(0,1fr)] gap-6 max-w-5xl">
       {/* ========== 左列 ========== */}
       <div className="space-y-6">
         {/* 行情状态 — 开关 + 间隔 */}