fix: 清理死代码 + 修复群组模式预算支出计算

- 清理 store 中未使用的 loading 状态（stats/budget/category/user）
- 清理 stats store 冗余类型重导出和 catch 重置逻辑
- 清理 transaction store 未使用的 currentPage
- 清理 api/group 未使用的 GroupDetail/GroupMember/getGroupDetail
- 删除无引用的 api/index.ts barrel 导出文件
- 删除后端未调用的 GET /groups/:id 群组详情路由
- 合并 stats 页面重复的 loadTabData 函数
- 修复预算页群组模式下只算个人支出（不传 group_id）

client/src/pages/budget/index.vue

@@ -77,8 +77,8 @@
 import { ref, onMounted } from 'vue'
 import { onShow } from '@dcloudio/uni-app'
 import { useBudgetStore } from '@/stores/budget'
-import { useStatsStore } from '@/stores/stats'
 import { useGroupStore } from '@/stores/group'
+import { getOverview } from '@/api/stats'
 import { waitForReady } from '@/utils/app-ready'
 import { formatAmount, getCurrentMonth } from '@/utils/format'
 import { statusBarHeight } from '@/utils/system'
@@ -87,7 +87,6 @@ import Numpad from '@/components/Numpad/Numpad.vue'
 import Icon from '@/components/Icon/Icon.vue'
 
 const budgetStore = useBudgetStore()
-const statsStore = useStatsStore()
 const groupStore = useGroupStore()
 
 const currentMonth = getCurrentMonth()
@@ -106,7 +105,6 @@ function formatPreset(val: number) {
 
 function syncBudgetData() {
   budget.value = budgetStore.budget
-  monthExpense.value = statsStore.overview.expense
   // 群组模式用 myAmount（个人预算），个人模式用 amount
   budgetAmount.value = budget.value
     ? (groupStore.isGroupMode ? (budget.value.myAmount || 0) : budget.value.amount)
@@ -116,13 +114,19 @@ function syncBudgetData() {
   }
 }
 
+/** 获取个人支出（不传 group_id，始终只算自己的消费） */
+async function fetchMyExpense() {
+  const data = await getOverview({ month: currentMonth, group_id: null })
+  monthExpense.value = Number(data?.expense) || 0
+}
+
 onMounted(async () => {
   await waitForReady()
   loading.value = true
   try {
     await Promise.all([
       budgetStore.fetchBudget(currentMonth),
-      statsStore.fetchOverview(currentMonth)
+      fetchMyExpense()
     ])
     syncBudgetData()
   } catch (e) {
@@ -139,7 +143,7 @@ onShow(async () => {
   try {
     await Promise.all([
       budgetStore.fetchBudget(currentMonth),
-      statsStore.fetchOverview(currentMonth)
+      fetchMyExpense()
     ])
     syncBudgetData()
   } catch {}

client/src/pages/stats/index.vue

@@ -236,7 +236,7 @@ onShow(() => {
 
 // Only re-fetch category/trend on tab switch; re-fetch all on month change
 watch(currentMonth, () => loadData())
-watch(tabType, () => loadTabData())
+watch(tabType, () => loadData(true))
 
 async function loadData(silent = false) {
   const seq = ++loadSeq
@@ -260,26 +260,6 @@ async function loadData(silent = false) {
   }
 }
 
-// Re-fetch all data when tab switches
-async function loadTabData() {
-  const seq = ++loadSeq
-  loadError.value = false
-  try {
-    await Promise.all([
-      statsStore.fetchOverview(currentMonth.value),
-      statsStore.fetchCategoryStats(currentMonth.value, tabType.value),
-      statsStore.fetchTrend(currentMonth.value, tabType.value),
-      fetchMaxSingle(),
-      fetchPrevMonthData()
-    ])
-    if (seq !== loadSeq) return
-  } catch (e) {
-    if (seq !== loadSeq) return
-    console.error('Stats tab load error:', e)
-    loadError.value = true
-  }
-}
-
 async function fetchMaxSingle() {
   try {
     const [y, m] = currentMonth.value.split('-').map(Number)