feat: refactor monolithic App.vue into modular Vue component architecture

- Extract 711-line App.vue into 15+ focused files across 5 directories
- Add data layer (icons, metrics, policies, auditTrail, requests)
- Add composables (useNavigation, useRequests, useChat, useToast)
- Add layout components (SidebarRail, TopBar, FilterBar)
- Add shared components (PanelHead, InfoRow, ToastNotification)
- Add business component (RequestTable) and 5 view components
- Extract global CSS to assets/styles/global.css
- Add start.sh with WSL/Windows cross-platform support
- Add .gitignore for node_modules, dist, and IDE dirs

src/composables/useRequests.js

@@ -0,0 +1,37 @@
+import { computed, reactive, ref } from 'vue'
+import { initialRequests } from '../data/requests.js'
+
+export function useRequests() {
+  const requests = ref(initialRequests)
+  const search = ref('')
+  const filters = reactive({ entity: '全部主体', category: '全部费用', risk: '全部风险' })
+  const ranges = ['今日', '本周', '本月']
+  const activeRange = ref('今日')
+
+  const filteredRequests = computed(() => {
+    const key = search.value.trim().toLowerCase()
+    return requests.value.filter((item) => {
+      const matchesSearch = !key || `${item.id}${item.person}${item.category}${item.risk}`.toLowerCase().includes(key)
+      const matchesCategory = filters.category === '全部费用' || item.category.includes(filters.category.replace('交通', ''))
+      const matchesRisk = filters.risk === '全部风险' || (filters.risk === '高风险' ? item.status === 'danger' : item.verdict.includes(filters.risk.replace('低风险', '通过')))
+      return matchesSearch && matchesCategory && matchesRisk
+    })
+  })
+
+  function approveRequest(request) {
+    request.verdict = '已通过'
+    request.status = 'success'
+    return `${request.id} 已标记为通过，审计日志已更新。`
+  }
+
+  function rejectRequest(request) {
+    request.verdict = '已退回补件'
+    request.status = 'danger'
+    return `${request.id} 已退回，系统将通知申请人补充材料。`
+  }
+
+  return {
+    requests, search, filters, ranges, activeRange,
+    filteredRequests, approveRequest, rejectRequest
+  }
+}