feat: 添加Neo4j图数据库支持及前端代码重构

- 新增 Neo4j 图数据库 handler、service、model
- 后端添加 SaveGraph API 接口
- 前端 Database.vue 重构，拆分为独立组件
- 新增 web/src/views/database/ 组件目录
- 删除临时文件 (temp_*.go)
- 添加 Neo4j 相关 API 需求文档

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/views/database/database.css

@@ -0,0 +1,75 @@
+/* Database View Styles */
+
+/* 搜索输入框 */
+.search-input {
+  @apply bg-dark-700 border border-dark-500 rounded-lg px-4 py-2.5 pl-10 text-white placeholder-gray-500 focus:outline-none focus:border-primary-cyan focus:ring-1 focus:ring-primary-cyan/30 transition-all;
+}
+
+/* 输入框 */
+.input-field {
+  @apply w-full bg-dark-700 border border-dark-500 rounded-lg px-4 py-2.5 text-white placeholder-gray-500 focus:outline-none focus:border-primary-cyan focus:ring-1 focus:ring-primary-cyan/30 transition-all;
+}
+
+/* 主要按钮 */
+.btn-primary {
+  @apply px-4 py-2 rounded-lg bg-gradient-to-r from-primary-cyan to-blue-500 text-white hover:from-cyan-500 hover:to-blue-600 transition-all flex items-center gap-2;
+}
+
+/* 次要按钮 */
+.btn-secondary {
+  @apply px-4 py-2 rounded-lg bg-dark-600 text-gray-300 hover:bg-dark-500 transition-all flex items-center gap-2;
+}
+
+/* 图标按钮 */
+.btn-icon {
+  @apply p-2 rounded-lg hover:bg-dark-600 transition-colors;
+}
+
+/* 表格行 */
+.table-row {
+  @apply border-b border-dark-600 hover:bg-dark-600/50 transition-colors;
+}
+
+/* 空状态 */
+.empty-state {
+  @apply py-16 text-center text-gray-500;
+}
+
+.empty-state-icon {
+  @apply text-4xl mb-4 block;
+}
+
+/* 表格复选框 */
+.table-checkbox {
+  @apply flex-shrink-0;
+}
+
+/* 弹窗遮罩 */
+.modal-overlay {
+  animation: fadeIn 0.2s ease-out;
+}
+
+/* 弹窗内容 */
+.modal-content {
+  animation: slideUp 0.3s ease-out;
+}
+
+@keyframes fadeIn {
+  from {
+    opacity: 0;
+  }
+  to {
+    opacity: 1;
+  }
+}
+
+@keyframes slideUp {
+  from {
+    opacity: 0;
+    transform: translateY(20px);
+  }
+  to {
+    opacity: 1;
+    transform: translateY(0);
+  }
+}