📦 添加虚拟环境和启动脚本

新增:
- backend/venv/ - Python 虚拟环境
- backend/start.sh - 启动脚本（使用虚拟环境）
- backend/requirements.txt - 依赖列表
- .gitignore - 忽略虚拟环境和缓存文件

说明:
- 每个项目使用独立虚拟环境
- 避免依赖冲突
- 启动脚本自动创建和激活虚拟环境

frontend/node_modules/eslint/lib/cli-engine/formatters/jslint-xml.js

@@ -0,0 +1,41 @@
+/**
+ * @fileoverview JSLint XML reporter
+ * @author Ian Christian Myers
+ */
+"use strict";
+
+const xmlEscape = require("../xml-escape");
+
+//------------------------------------------------------------------------------
+// Public Interface
+//------------------------------------------------------------------------------
+
+module.exports = function(results) {
+
+    let output = "";
+
+    output += "<?xml version=\"1.0\" encoding=\"utf-8\"?>";
+    output += "<jslint>";
+
+    results.forEach(result => {
+        const messages = result.messages;
+
+        output += `<file name="${result.filePath}">`;
+
+        messages.forEach(message => {
+            output += [
+                `<issue line="${message.line}"`,
+                `char="${message.column}"`,
+                `evidence="${xmlEscape(message.source || "")}"`,
+                `reason="${xmlEscape(message.message || "")}${message.ruleId ? ` (${message.ruleId})` : ""}" />`
+            ].join(" ");
+        });
+
+        output += "</file>";
+
+    });
+
+    output += "</jslint>";
+
+    return output;
+};