清理市场概览残留：删除 MarketOverviewBanner+refresh_policy 中的 marketOverview 条目

frontend/lib/refresh-policy.ts

@@ -0,0 +1,13 @@
+export const DASHBOARD_REFRESH_POLICY_SEC = {
+  observation: 60,
+  metar: 5 * 60,
+  scanRows: 5 * 60,
+  model: 30 * 60,
+} as const;
+
+export const DASHBOARD_REFRESH_POLICY_MS = {
+  observation: DASHBOARD_REFRESH_POLICY_SEC.observation * 1000,
+  metar: DASHBOARD_REFRESH_POLICY_SEC.metar * 1000,
+  scanRows: DASHBOARD_REFRESH_POLICY_SEC.scanRows * 1000,
+  model: DASHBOARD_REFRESH_POLICY_SEC.model * 1000,
+} as const;