新增: 初始化 DevFlow 项目仓库

Tauri 2 + Vue 3 + Vite 6 桌面应用，Rust workspace 含 13 个 crate
(df-ai / df-storage / df-workflow / df-core / df-execute 等)。
核心能力：AI 聊天 agentic 循环(工具调用+人工审批)、工作流引擎、
任务/想法/项目/阶段管理、可追溯性，及配套前端组件。

crates/df-nodes/src/http_node.rs

@@ -0,0 +1,43 @@
+//! HTTP 节点 — 发起 HTTP 请求
+
+use async_trait::async_trait;
+use df_workflow::node::{Node, NodeContext, NodeOutput, NodeResult, NodeSchema};
+
+/// HTTP 节点
+pub struct HttpNode;
+
+#[async_trait]
+impl Node for HttpNode {
+    async fn execute(&self, _ctx: NodeContext) -> NodeResult {
+        // TODO: 实现HTTP请求逻辑
+        tracing::info!("HttpNode 执行: 发送 HTTP 请求");
+        Ok(NodeOutput::empty())
+    }
+
+    fn schema(&self) -> NodeSchema {
+        NodeSchema {
+            params: serde_json::json!({
+                "type": "object",
+                "properties": {
+                    "method": { "type": "string", "enum": ["GET", "POST", "PUT", "DELETE"] },
+                    "url": { "type": "string" },
+                    "headers": { "type": "object" },
+                    "body": {}
+                },
+                "required": ["method", "url"]
+            }),
+            output: serde_json::json!({
+                "type": "object",
+                "properties": {
+                    "status": { "type": "integer" },
+                    "body": {},
+                    "headers": { "type": "object" }
+                }
+            }),
+        }
+    }
+
+    fn node_type(&self) -> &str {
+        "http"
+    }
+}