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/App.vue

@@ -0,0 +1,122 @@
+<template>
+  <div class="app">
+    <SidebarRail
+      :nav-items="navItems"
+      :active-view="activeView"
+      @navigate="setView"
+      @open-chat="openChat"
+    />
+
+    <main class="main">
+      <TopBar
+        :current-view="currentView"
+        :search="search"
+        @update:search="search = $event"
+        @batch-approve="toast('已筛出 23 个低风险单据，可进入批量通过确认。')"
+        @open-chat="openChat"
+      />
+
+      <FilterBar
+        v-if="activeView !== 'chat'"
+        :filters="filters"
+        :ranges="ranges"
+        :active-range="activeRange"
+        @update:active-range="activeRange = $event"
+      />
+
+      <section class="workarea">
+        <OverviewView
+          v-if="activeView === 'overview'"
+          :filtered-requests="filteredRequests"
+          @ask="openChat"
+          @approve="handleApprove"
+          @reject="handleReject"
+        />
+
+        <ChatView
+          v-else-if="activeView === 'chat'"
+          ref="chatViewRef"
+          :messages="messages"
+          :uploaded-files="uploadedFiles"
+          :active-case="activeCase"
+          :quick-prompts="prompts"
+          :draft="draft"
+          :message-list="messageList"
+          @send="sendMessage"
+          @upload="handleUpload"
+          @draft="draft = $event"
+          @approve-case="toast(`${activeCase?.id} 已生成通过意见。`)"
+          @reject-case="toast(`${activeCase?.id} 已转人工复核。`)"
+        />
+
+        <RequestsView
+          v-else-if="activeView === 'requests'"
+          :filtered-requests="filteredRequests"
+          @ask="openChat"
+          @approve="handleApprove"
+          @reject="handleReject"
+        />
+
+        <PoliciesView v-else-if="activeView === 'policies'" />
+
+        <AuditView v-else />
+      </section>
+    </main>
+
+    <ToastNotification :toast-text="toastText" />
+  </div>
+</template>
+
+<script setup>
+import './assets/styles/global.css'
+
+import SidebarRail from './components/layout/SidebarRail.vue'
+import TopBar from './components/layout/TopBar.vue'
+import FilterBar from './components/layout/FilterBar.vue'
+import ToastNotification from './components/shared/ToastNotification.vue'
+import OverviewView from './views/OverviewView.vue'
+import ChatView from './views/ChatView.vue'
+import RequestsView from './views/RequestsView.vue'
+import PoliciesView from './views/PoliciesView.vue'
+import AuditView from './views/AuditView.vue'
+
+import { useNavigation, navItems } from './composables/useNavigation.js'
+import { useRequests } from './composables/useRequests.js'
+import { useChat } from './composables/useChat.js'
+import { useToast } from './composables/useToast.js'
+
+const { activeView, currentView, setView } = useNavigation()
+const { requests, search, filters, ranges, activeRange, filteredRequests, approveRequest, rejectRequest } = useRequests()
+const { messages, draft, uploadedFiles, messageList, activeCase, prompts, sendMessage, handleUpload, openChat } = useChat(activeView)
+const { toastText, toast } = useToast()
+
+function handleApprove(request) {
+  const msg = approveRequest(request)
+  toast(msg)
+}
+
+function handleReject(request) {
+  const msg = rejectRequest(request)
+  toast(msg)
+}
+</script>
+
+<style scoped>
+.app {
+  min-height: 100dvh;
+  display: grid;
+  grid-template-columns: 76px minmax(0, 1fr);
+  background:
+    radial-gradient(circle at 22% -12%, rgba(51,92,255,.10), transparent 34%),
+    linear-gradient(180deg, #fff 0, var(--bg) 260px);
+}
+.main { min-width: 0; display: grid; grid-template-rows: auto auto minmax(0, 1fr); }
+.workarea { overflow: auto; padding: 22px 28px 34px; }
+
+@media (max-width: 1180px) {
+  .app { grid-template-columns: 72px minmax(0, 1fr); }
+}
+@media (max-width: 760px) {
+  .app { display: block; }
+}
+</style>