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/useChat.js

@@ -0,0 +1,63 @@
+import { nextTick, ref } from 'vue'
+import { initialMessages, prompts } from '../data/requests.js'
+
+export function useChat(activeView) {
+  const messages = ref([...initialMessages])
+  const draft = ref('')
+  const uploadedFiles = ref([])
+  const messageList = ref(null)
+  const activeCase = ref(null)
+
+  function agentReply(text) {
+    const c = activeCase.value
+    if (!c) return '建议先核对政策阈值和附件完整性，再决定通过、退回补件或转人工复核。'
+    if (text.includes('审批')) return `${c.id} 建议审批意见：发票验真通过，费用归属与预算中心匹配；${c.risk} 已触发规则提示，建议保留业务说明后通过。`
+    if (text.includes('补件')) return '补件优先级：业务目的说明、行程或客户名单、直属经理确认记录。'
+    if (text.includes('拦截')) return `拦截原因是 ${c.risk}，该风险需要财务复核并留下制度依据。`
+    if (text.includes('审计')) return `审计摘要：${c.person} 提交 ${c.amount} 报销，命中 ${c.risk}，系统已保留 AI 判断。`
+    return '建议先核对政策阈值和附件完整性，再决定通过、退回补件或转人工复核。'
+  }
+
+  function scrollToBottom() {
+    nextTick(() => messageList.value?.scrollTo({ top: messageList.value.scrollHeight, behavior: 'smooth' }))
+  }
+
+  function sendMessage() {
+    const text = draft.value.trim()
+    if (!text) return false
+    messages.value.push({ id: Date.now(), role: 'user', text })
+    draft.value = ''
+    setTimeout(() => {
+      messages.value.push({ id: Date.now() + 1, role: 'agent', text: agentReply(text) })
+      scrollToBottom()
+    }, 260)
+    return true
+  }
+
+  function handleUpload(event) {
+    uploadedFiles.value = Array.from(event.target.files ?? []).map((file) => ({
+      name: file.name,
+      size: file.size
+    }))
+    if (uploadedFiles.value.length) {
+      const names = uploadedFiles.value.map((file) => file.name).join('、')
+      messages.value.push({
+        id: Date.now(),
+        role: 'agent',
+        text: `已接收 ${uploadedFiles.value.length} 个附件：${names}。我会优先核对发票验真、费用标准、预算归属和必备审批材料。`
+      })
+      scrollToBottom()
+    }
+  }
+
+  function openChat(request) {
+    activeCase.value = request
+    activeView.value = 'chat'
+    nextTick(() => messageList.value?.scrollTo({ top: messageList.value.scrollHeight }))
+  }
+
+  return {
+    messages, draft, uploadedFiles, messageList, activeCase, prompts,
+    sendMessage, handleUpload, openChat, scrollToBottom
+  }
+}