fix(water): preserve monitoring data on request failures (#8)

src/views/subSystem/waterSupply/components/WaterMonitoringPage.vue

@@ -219,7 +219,6 @@
             normalized.records = normalized.records.map(row => normalizeMonitoringRecord(row, props.metric, props.monitorType))
             page.value = normalized
         } catch (error) {
-            page.value = {records: [], total: 0}
             loadError.value = true
             console.warn(`[${props.title}] 数据加载失败`, error)
         } finally {
@@ -257,14 +256,18 @@
     async function showTrend(row) {
         current.value = row
         trendVisible.value = true
-        await loadTrend()
+        await loadTrend(true)
     }
 
-    async function loadTrend() {
+    async function loadTrend(resetTrend = false) {
         if (!current.value?.id) return
         trendLoading.value = true
         trendError.value = false
-        trendRecords.value = []
+        if (resetTrend) {
+            trendRecords.value = []
+            chart?.dispose()
+            chart = undefined
+        }
         try {
             const response = await props.trend(current.value.id, buildTrendQuery(query.value.timeRange))
             const data = unwrapResponse(response)
@@ -274,8 +277,10 @@
             renderTrend()
         } catch (error) {
             trendError.value = true
-            chart?.dispose()
-            chart = undefined
+            if (resetTrend) {
+                chart?.dispose()
+                chart = undefined
+            }
             console.warn(`[${props.title}] 趋势数据加载失败`, error)
         } finally {
             trendLoading.value = false