refactor(dashboard): useDashboardData 提取 SECTION_FETCHERS 模块级单例

代码评审建议：loadAll 与 refresh 各有一份相同的 7 项 fetcher 映射，
且 refresh 每次调用都重建对象。提取为模块级单例后：
- 消除重复（单一信源）
- 节省每次 refresh 的对象分配
- loadAll 用 Object.entries 驱动而非手写 7 行

frontend/composables/useDashboardData.js

@@ -1,6 +1,17 @@
 import { ref, computed } from 'vue'
 import { dashboardApi } from '@/utils/api'
 
+// section 名 → fetcher 映射，模块级单例，loadAll 与 refresh 复用
+const SECTION_FETCHERS = {
+  today: dashboardApi.getTodayOverview,
+  curve: dashboardApi.get7DayIncomeCurve,
+  exhibition: dashboardApi.getExhibitionSummary,
+  likeIncome: dashboardApi.getLikeIncomeByLevel,
+  topAssets: dashboardApi.getTopAssets,
+  levels: dashboardApi.getLevelDistribution,
+  upgrades: dashboardApi.getUpgradeProgress,
+}
+
 /**
  * 数据看板聚合 composable
  * - 7 个接口并发（Promise.allSettled，单失败不阻塞）
@@ -69,15 +80,11 @@ export function useDashboardData({ starId = null } = {}) {
     if (!force && Date.now() - lastFetched.value < STALE_MS) return
     loading.value.overall = true
     try {
-      await Promise.allSettled([
-        loadSection('today', dashboardApi.getTodayOverview),
-        loadSection('curve', dashboardApi.get7DayIncomeCurve),
-        loadSection('exhibition', dashboardApi.getExhibitionSummary),
-        loadSection('likeIncome', dashboardApi.getLikeIncomeByLevel),
-        loadSection('topAssets', dashboardApi.getTopAssets),
-        loadSection('levels', dashboardApi.getLevelDistribution),
-        loadSection('upgrades', dashboardApi.getUpgradeProgress),
-      ])
+      await Promise.allSettled(
+        Object.entries(SECTION_FETCHERS).map(([section, fetcher]) =>
+          loadSection(section, fetcher)
+        )
+      )
       lastFetched.value = Date.now()
     } finally {
       loading.value.overall = false
@@ -87,17 +94,9 @@ export function useDashboardData({ starId = null } = {}) {
   // 局部刷新：refresh('curve') 只刷一个；refresh() 全量 cache-aware；refresh(true) 全量强制
   async function refresh(section, force = false) {
     if (section) {
-      const fetcherMap = {
-        today: dashboardApi.getTodayOverview,
-        curve: dashboardApi.get7DayIncomeCurve,
-        exhibition: dashboardApi.getExhibitionSummary,
-        likeIncome: dashboardApi.getLikeIncomeByLevel,
-        topAssets: dashboardApi.getTopAssets,
-        levels: dashboardApi.getLevelDistribution,
-        upgrades: dashboardApi.getUpgradeProgress,
-      }
-      if (!fetcherMap[section]) return
-      return loadSection(section, fetcherMap[section])
+      const fetcher = SECTION_FETCHERS[section]
+      if (!fetcher) return
+      return loadSection(section, fetcher)
     }
     return loadAll(force)
   }