feat: AIHR 智能人力资源管理系统初始提交

- 员工花名册管理（加密存储、导入导出）
- 薪酬管理（发薪批次、薪酬模版、加班费计算、工资条）
- 社保公积金（多城市配置、版本管理、基数调整）
- 解聘管理（6步流程、证据链、工作交接）
- AI 助手（合同审查、风险预测、RAG 知识库）
- Dashboard 仪表盘
- 设置与通知

frontend/src/index.css

@@ -0,0 +1,52 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+@layer base {
+  body {
+    @apply bg-surface text-gray-900 antialiased;
+    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
+    font-size: 16px;
+    line-height: 1.5;
+  }
+
+  * {
+    @apply box-border;
+  }
+
+  h1 { @apply text-lg font-semibold; }
+  h2 { @apply text-base font-semibold; }
+  h3 { @apply text-sm font-medium; }
+}
+
+@layer components {
+  .btn {
+    @apply inline-flex items-center justify-center px-3 py-1.5 rounded font-medium text-sm transition-colors disabled:opacity-50 disabled:cursor-not-allowed;
+  }
+  .btn-primary {
+    @apply btn bg-primary text-white hover:bg-primary-dark;
+  }
+  .btn-secondary {
+    @apply btn bg-gray-100 text-gray-700 hover:bg-gray-200;
+  }
+  .btn-danger {
+    @apply btn bg-danger text-white hover:bg-red-700;
+  }
+  .card {
+    @apply bg-white rounded-lg shadow-sm border border-gray-200 p-4;
+  }
+  .input {
+    @apply w-full px-2.5 py-1.5 rounded-md border border-gray-300 focus:outline-none focus:ring-2 focus:ring-primary focus:border-transparent text-sm;
+  }
+  .label {
+    @apply block text-sm font-medium text-gray-700 mb-1;
+  }
+}
+
+@media print {
+  header, nav, .no-print { display: none !important; }
+  main { padding: 0 !important; max-width: 100% !important; }
+  .card { box-shadow: none !important; border: 1px solid #ccc !important; break-inside: avoid; }
+  body { background: white !important; }
+  a { color: inherit !important; text-decoration: none !important; }
+}