📦 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/visualstudio.js

@@ -0,0 +1,63 @@
+/**
+ * @fileoverview Visual Studio compatible formatter
+ * @author Ronald Pijnacker
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Helper Functions
+//------------------------------------------------------------------------------
+
+/**
+ * Returns the severity of warning or error
+ * @param {Object} message message object to examine
+ * @returns {string} severity level
+ * @private
+ */
+function getMessageType(message) {
+    if (message.fatal || message.severity === 2) {
+        return "error";
+    }
+    return "warning";
+
+}
+
+
+//------------------------------------------------------------------------------
+// Public Interface
+//------------------------------------------------------------------------------
+
+module.exports = function(results) {
+
+    let output = "",
+        total = 0;
+
+    results.forEach(result => {
+
+        const messages = result.messages;
+
+        total += messages.length;
+
+        messages.forEach(message => {
+
+            output += result.filePath;
+            output += `(${message.line || 0}`;
+            output += message.column ? `,${message.column}` : "";
+            output += `): ${getMessageType(message)}`;
+            output += message.ruleId ? ` ${message.ruleId}` : "";
+            output += ` : ${message.message}`;
+            output += "\n";
+
+        });
+
+    });
+
+    if (total === 0) {
+        output += "no problems";
+    } else {
+        output += `\n${total} problem${total !== 1 ? "s" : ""}`;
+    }
+
+    return output;
+};