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/components/layout/TopBar.vue

@@ -0,0 +1,56 @@
+<template>
+  <header class="topbar">
+    <div>
+      <div class="eyebrow">Global finance operations</div>
+      <h1>{{ currentView.title }}</h1>
+      <p>{{ currentView.desc }}</p>
+    </div>
+    <div class="top-actions">
+      <label class="search">
+        <span v-html="searchIcon"></span>
+        <input :value="search" type="search" placeholder="搜索申请人、单号、费用类型" @input="emit('update:search', $event.target.value)" />
+      </label>
+      <button class="btn" type="button" @click="emit('batchApprove')">
+        <span v-html="checkIcon"></span>
+        批量通过
+      </button>
+      <button class="btn primary" type="button" @click="emit('openChat')">
+        <span v-html="messageIcon"></span>
+        合规对话
+      </button>
+    </div>
+  </header>
+</template>
+
+<script setup>
+import { icons } from '../../data/icons.js'
+
+defineProps({
+  currentView: { type: Object, required: true },
+  search: { type: String, default: '' }
+})
+
+const emit = defineEmits(['update:search', 'batchApprove', 'openChat'])
+
+const searchIcon = icons.search
+const checkIcon = icons.check
+const messageIcon = icons.message
+</script>
+
+<style scoped>
+.topbar {
+  display: flex;
+  justify-content: space-between;
+  gap: 24px;
+  padding: 22px 28px;
+  border-bottom: 1px solid var(--line);
+  background: rgba(255,255,255,.9);
+  backdrop-filter: blur(14px);
+}
+.topbar p { margin-top: 6px; color: var(--muted); font-size: 13px; }
+.top-actions { display: flex; align-items: center; justify-content: flex-end; gap: 10px; flex-wrap: wrap; }
+.search { position: relative; min-width: 300px; }
+.search span { position: absolute; left: 13px; top: 50%; width: 18px; height: 18px; transform: translateY(-50%); color: var(--muted); }
+.search span svg { width: 18px; height: 18px; stroke: currentColor; stroke-width: 2; fill: none; stroke-linecap: round; stroke-linejoin: round; }
+.search input { width: 100%; height: 42px; padding: 0 14px 0 40px; border: 1px solid var(--line); border-radius: var(--radius); }
+</style>