feat: phase 3 - ledger and asset management

Add group expense tracking (ledger) and public asset inventory (asset) features.
Ledger supports income/expense recording with monthly summary. Asset tracks
group equipment with free-form holder transfer. Both are independent pages
accessible from GroupView navigation.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/views/LedgerView.vue

@@ -0,0 +1,105 @@
+<!-- src/views/LedgerView.vue -->
+<script setup lang="ts">
+import { onMounted, computed } from 'vue'
+import { useRoute } from 'vue-router'
+import { useGroupStore } from '@/stores/group'
+import { useLedgerStore } from '@/stores/ledger'
+import LedgerList from '@/components/ledger/LedgerList.vue'
+import { ArrowLeft } from '@element-plus/icons-vue'
+
+const route = useRoute()
+const groupStore = useGroupStore()
+const ledgerStore = useLedgerStore()
+const groupId = route.params.groupId as string
+
+const group = computed(() => groupStore.currentGroup)
+
+onMounted(async () => {
+  await groupStore.setCurrentGroup(groupId)
+  await ledgerStore.loadLedgers(groupId)
+})
+</script>
+
+<template>
+  <div class="ledger-view">
+    <!-- 页面头部 -->
+    <section class="page-header">
+      <router-link :to="`/group/${groupId}`" class="back-link">
+        <el-icon><ArrowLeft /></el-icon> 返回群组
+      </router-link>
+      <div class="header-content">
+        <h1 class="page-title">账目管理</h1>
+        <span class="group-badge">{{ group?.name }}</span>
+      </div>
+    </section>
+
+    <!-- 账目列表 -->
+    <LedgerList />
+  </div>
+</template>
+
+<style scoped>
+.ledger-view {
+  width: 100%;
+  display: flex;
+  flex-direction: column;
+  gap: 20px;
+}
+
+.page-header {
+  padding: 20px 24px;
+  background: var(--gg-bg-card);
+  border: 1px solid var(--gg-border);
+  border-radius: var(--gg-radius-lg);
+  position: relative;
+  overflow: hidden;
+}
+
+.page-header::before {
+  content: '';
+  position: absolute;
+  top: 0;
+  left: 0;
+  right: 0;
+  height: 3px;
+  background: var(--gg-gradient);
+}
+
+.back-link {
+  display: inline-flex;
+  align-items: center;
+  gap: 4px;
+  color: var(--gg-text-muted);
+  text-decoration: none;
+  font-size: 13px;
+  font-weight: 500;
+  transition: color 0.2s;
+  margin-bottom: 12px;
+}
+
+.back-link:hover {
+  color: var(--gg-primary);
+}
+
+.header-content {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+}
+
+.page-title {
+  font-size: 22px;
+  font-weight: 700;
+  margin: 0;
+  color: var(--gg-text);
+}
+
+.group-badge {
+  font-size: 13px;
+  padding: 4px 12px;
+  border-radius: 20px;
+  background: rgba(5, 150, 105, 0.15);
+  color: var(--gg-primary-light);
+  font-weight: 500;
+}
+</style>