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/composables/useApi.ts

@@ -0,0 +1,125 @@
+import { ref, computed } from 'vue'
+import { ElMessage } from 'element-plus'
+
+/**
+ * API 请求封装
+ * @param apiFunc - API 请求函数
+ * @param options - 配置选项
+ */
+export function useApi<T = any>(
+  apiFunc: (...args: any[]) => Promise<Response>,
+  options: {
+    showError?: boolean
+    showSuccess?: boolean
+    successMessage?: string
+    errorMessage?: string
+  } = {}
+) {
+  const { showError = true, showSuccess = false, successMessage, errorMessage } = options
+
+  const loading = ref(false)
+  const data = ref<T | null>(null)
+  const error = ref<Error | null>(null)
+
+  const execute = async (...args: any[]) => {
+    loading.value = true
+    error.value = null
+
+    try {
+      const response = await apiFunc(...args)
+
+      if (!response.ok) {
+        throw new Error(`HTTP ${response.status}`)
+      }
+
+      const result = await response.json()
+
+      if (result.success || response.ok) {
+        data.value = result
+
+        if (showSuccess) {
+          ElMessage.success(successMessage || result.message || '操作成功')
+        }
+
+        return result
+      } else {
+        if (showError) {
+          ElMessage.error(errorMessage || result.message || '操作失败')
+        }
+        throw new Error(result.message || '操作失败')
+      }
+    } catch (err: any) {
+      error.value = err
+
+      if (showError) {
+        ElMessage.error(errorMessage || err.message || '请求失败')
+      }
+
+      throw err
+    } finally {
+      loading.value = false
+    }
+  }
+
+  return {
+    loading: computed(() => loading.value),
+    data: computed(() => data.value),
+    error: computed(() => error.value),
+    execute,
+  }
+}
+
+/**
+ * 简单的 CRUD 操作封装
+ */
+export function useCrud<T = any>(baseUrl: string) {
+  const API_BASE = baseUrl
+
+  const fetchList = async (params?: any) => {
+    const query = params ? '?' + new URLSearchParams(params).toString() : ''
+    const response = await fetch(`${API_BASE}${query}`)
+    const result = await response.json()
+    return result
+  }
+
+  const fetchById = async (id: string) => {
+    const response = await fetch(`${API_BASE}/${id}`)
+    const result = await response.json()
+    return result
+  }
+
+  const create = async (data: Partial<T>) => {
+    const response = await fetch(API_BASE, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify(data),
+    })
+    const result = await response.json()
+    return result
+  }
+
+  const update = async (id: string, data: Partial<T>) => {
+    const response = await fetch(`${API_BASE}/${id}`, {
+      method: 'PUT',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify(data),
+    })
+    const result = await response.json()
+    return result
+  }
+
+  const remove = async (id: string) => {
+    const response = await fetch(`${API_BASE}/${id}`, {
+      method: 'DELETE',
+    })
+    return response.ok
+  }
+
+  return {
+    fetchList,
+    fetchById,
+    create,
+    update,
+    remove,
+  }
+}