📦 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/adjust-sourcemap-loader/lib/process/decode-sources-with.js

@@ -0,0 +1,78 @@
+'use strict';
+
+var getFieldAsFn = require('./get-field-as-fn');
+
+/**
+ * Create a decoder for input sources using the given codec hash
+ * @this {object} A loader or compilation
+ * @param {Array.<object>} codecs A list of codecs, each with a `decode` function
+ * @param {boolean} mustDecode Return an error for a source that is not decoded
+ * @returns {function(string):string|Error} A decode function that returns an absolute path or else an Error
+ */
+function decodeSourcesWith(codecs, mustDecode) {
+  /* jshint validthis:true */
+  var context = this;
+
+  // get a list of valid decoders
+  var candidates = [].concat(codecs)
+    .reduce(reduceValidDecoder.bind(null, codecs), []);
+
+  /**
+   * Attempt to decode the given source path using the previously supplied codecs
+   * @param {string} inputSource A source path from a source map
+   * @returns {Error|string|undefined} An absolute path if decoded else an error if encountered else undefined
+   */
+  return function decode(inputSource) {
+
+    // attempt all candidates until a match
+    for (var i = 0, decoded = null; i < candidates.length && !decoded; i++) {
+
+      // call the decoder
+      try {
+        decoded = candidates[i].decode.call(context, inputSource);
+      }
+      catch (exception) {
+        return getNamedError(exception);
+      }
+
+      // match implies a return value
+      if (decoded) {
+
+        // abstract sources cannot be decoded, only validated
+        if (candidates[i].abstract) {
+          return undefined;
+        }
+        // non-string implies error
+        if (typeof decoded !== 'string') {
+          return getNamedError('Decoder returned a truthy value but it is not a string:\n' + decoded);
+        }
+        // otherwise success
+        else {
+          return decoded;
+        }
+      }
+    }
+
+    // default is undefined or error
+    return mustDecode ? new Error('No viable decoder for source: ' + inputSource) : undefined;
+
+    function getNamedError(details) {
+      var name    = candidates[i].name || '(unnamed)',
+          message = [
+            'Decoding with codec: ' + name,
+            'Incoming source: ' + inputSource,
+            details && (details.stack ? details.stack : details)
+          ]
+            .filter(Boolean)
+            .join('\n');
+      return new Error(message);
+    }
+  };
+}
+
+module.exports = decodeSourcesWith;
+
+function reduceValidDecoder(reduced, codec) {
+  var decoder = getFieldAsFn('decode')(codec);
+  return decoder ? reduced.concat(codec) : reduced;
+}