📦 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/acorn-import-phases/src/index.cjs

@@ -0,0 +1,5 @@
+const { plugin } = require("./plugin.cjs");
+
+module.exports = function (options = {}) {
+  return (Parser) => plugin(options, Parser, (Parser.acorn || require("acorn")).tokTypes);
+};

frontend/node_modules/acorn-import-phases/src/index.d.cts

@@ -0,0 +1,9 @@
+import { Parser } from "acorn";
+
+interface Options {
+  source?: boolean;
+  defer?: boolean;
+}
+
+declare function acornImportPhases(options?: Options): (BaseParser: typeof Parser) => typeof Parser;
+export = acornImportPhases;

frontend/node_modules/acorn-import-phases/src/index.d.mts

@@ -0,0 +1,8 @@
+import { Parser } from "acorn";
+
+interface Options {
+  source?: boolean;
+  defer?: boolean;
+}
+
+export default function acornImportPhases(options?: Options): (BaseParser: typeof Parser) => typeof Parser;

frontend/node_modules/acorn-import-phases/src/index.js

@@ -0,0 +1,6 @@
+import { tokTypes } from "acorn";
+import { plugin } from "./plugin.cjs";
+
+export default function (options = {}) {
+  return Parser => plugin(options, Parser, Parser.acorn ? Parser.acorn.tokTypes : tokTypes);
+}

frontend/node_modules/acorn-import-phases/src/plugin.cjs

@@ -0,0 +1,125 @@
+/**
+ * @param {{ defer?: boolean, source?: boolean }} options
+ * @param {typeof import("acorn").Parser} Parser
+ * @param {typeof import("acorn").tokTypes} acorn
+ */
+exports.plugin = function acornImportPhase(options, Parser, tt) {
+  return class extends Parser {
+    parseImport(node) {
+      this._phase = null;
+      const result = super.parseImport(node);
+      if (this._phase) {
+        node.phase = this._phase;
+      }
+      return result;
+    }
+
+    parseImportSpecifiers() {
+      let phase =
+        options.defer !== false && this.isContextual("defer")
+          ? "defer"
+          : options.source !== false && this.isContextual("source")
+          ? "source"
+          : null;
+      if (!phase) return super.parseImportSpecifiers();
+
+      const phaseId = this.parseIdent();
+      if (this.isContextual("from") || this.type === tt.comma) {
+        const defaultSpecifier = this.startNodeAt(phaseId.start, phaseId.loc && phaseId.loc.start);
+        defaultSpecifier.local = phaseId;
+        this.checkLValSimple(phaseId, /* BIND_LEXICAL */ 2);
+
+        const nodes = [this.finishNode(defaultSpecifier, "ImportDefaultSpecifier")];
+        if (this.eat(tt.comma)) {
+          if (this.type !== tt.star && this.type !== tt.braceL) {
+            this.unexpected();
+          }
+          nodes.push(...super.parseImportSpecifiers());
+        }
+        return nodes;
+      }
+
+      this._phase = phase;
+
+      if (phase === "defer") {
+        if (this.type !== tt.star) {
+          this.raiseRecoverable(
+            phaseId.start,
+            "'import defer' can only be used with namespace imports ('import defer * as identifierName from ...')."
+          );
+        }
+      } else if (phase === "source") {
+        if (this.type !== tt.name) {
+          this.raiseRecoverable(
+            phaseId.start,
+            "'import source' can only be used with direct identifier specifier imports."
+          );
+        }
+      }
+
+      const specifiers =  super.parseImportSpecifiers();
+
+      if (phase === "source" && specifiers.some(s => s.type !== "ImportDefaultSpecifier")) {
+        this.raiseRecoverable(
+          phaseId.start,
+          `'import source' can only be used with direct identifier specifier imports ('import source identifierName from ...').`
+        );
+      }
+
+      return specifiers;
+    }
+
+    parseExprImport(forNew) {
+      const node = super.parseExprImport(forNew);
+
+      if (node.type === "MetaProperty" && (node.property.name === "defer" || node.property.name === "source")) {
+        if (this.type === tt.parenL) {
+          const dynImport = this.parseDynamicImport(this.startNodeAt(node.start, node.loc && node.loc.start));
+          dynImport.phase = node.property.name;
+          return dynImport;
+        } else {
+          this.raiseRecoverable(
+            node.start,
+            `'import.${node.property.name}' can only be used in a dynamic import.`
+          );
+        }
+      }
+
+      return node;
+    }
+
+    parseImportMeta(node) {
+      this.next();
+
+      var containsEsc = this.containsEsc;
+      node.property = this.parseIdent(true);
+
+      const { name } = node.property;
+
+      if (name !== "meta" && name !== "defer" && name !== "source") {
+        this.raiseRecoverable(
+          node.property.start,
+          "The only valid meta property for import is 'import.meta'"
+        );
+      }
+      if (containsEsc) {
+        this.raiseRecoverable(
+          node.start,
+          `'import.${name}' must not contain escaped characters`
+        );
+      }
+      if (
+        name === "meta" &&
+        this.options.sourceType !== "module" &&
+        !this.options.allowImportExportEverywhere
+      ) {
+        this.raiseRecoverable(
+          node.start,
+          "Cannot use 'import.meta' outside a module"
+        );
+      }
+
+      return this.finishNode(node, "MetaProperty");
+    }
+  };
+};