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>

server/cmd/api/main.go

@@ -79,10 +79,12 @@ func main() {
 	// 5. 初始化 Service
 	dbService := service.NewDatabaseService(dbRepo, subTableRepo)
 	subTableService := service.NewSubTableService(subTableRepo, dbRepo)
+	neo4jService := service.NewNeo4jService(dbRepo)
 
 	// 6. 初始化 Handler
 	dbHandler := handler.NewDatabaseHandler(dbService)
 	subTableHandler := handler.NewSubTableHandler(subTableService)
+	neo4jHandler := handler.NewNeo4jHandler(neo4jService)
 	systemHandler := handler.NewSystemHandler()
 
 	// 7. 设置路由
@@ -137,6 +139,7 @@ func main() {
 		databaseGroup.POST("/add", dbHandler.Create)
 		databaseGroup.PUT("/:id", dbHandler.Update)
 		databaseGroup.DELETE("/:id", dbHandler.Delete)
+		databaseGroup.POST("/graph/save", dbHandler.SaveGraph)
 	}
 
 	// 子表映射管理模块
@@ -151,6 +154,15 @@ func main() {
 		subTableGroup.DELETE("/:id", subTableHandler.Delete)
 	}
 
+	// Neo4j 连接管理模块
+	neo4jGroup := r.Group("/neo4j")
+	{
+		neo4jGroup.POST("/check", neo4jHandler.Check)
+		neo4jGroup.POST("/graphs", neo4jHandler.GetGraphs)
+		neo4jGroup.POST("/nodes", neo4jHandler.GetNodes)
+		neo4jGroup.POST("/relationships", neo4jHandler.GetRelationships)
+	}
+
 	// 系统信息模块
 	r.GET("/system/info", systemHandler.GetSystemInfo)