feat: 添加Chrome插件兜底支持，解决第三方插件401错误问题

• 新增browserFallback中间件，自动识别并处理Chrome插件请求
• 增强CORS支持，明确允许chrome-extension://来源
• 优化请求头过滤，移除可能触发Claude CORS检查的浏览器头信息
• 完善401错误处理逻辑，避免因临时token问题导致账号被错误停用

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/middleware/browserFallback.js

@@ -0,0 +1,50 @@
+const logger = require('../utils/logger')
+
+/**
+ * 浏览器/Chrome插件兜底中间件
+ * 专门处理第三方插件的兼容性问题
+ */
+const browserFallbackMiddleware = (req, res, next) => {
+  const userAgent = req.headers['user-agent'] || ''
+  const origin = req.headers['origin'] || ''
+  const authHeader = req.headers['authorization'] || req.headers['x-api-key'] || ''
+  
+  // 检查是否为Chrome插件或浏览器请求
+  const isChromeExtension = origin.startsWith('chrome-extension://')
+  const isBrowserRequest = userAgent.includes('Mozilla/') && userAgent.includes('Chrome/')
+  const hasApiKey = authHeader.startsWith('cr_') // 我们的API Key格式
+  
+  if ((isChromeExtension || isBrowserRequest) && hasApiKey) {
+    // 为Chrome插件请求添加特殊标记
+    req.isBrowserFallback = true
+    req.originalUserAgent = userAgent
+    
+    // 🆕 关键修改：伪装成claude-cli请求以绕过客户端限制
+    req.headers['user-agent'] = 'claude-cli/1.0.110 (external, cli, browser-fallback)'
+    
+    // 确保设置正确的认证头
+    if (!req.headers['authorization'] && req.headers['x-api-key']) {
+      req.headers['authorization'] = `Bearer ${req.headers['x-api-key']}`
+    }
+    
+    // 添加必要的Anthropic头
+    if (!req.headers['anthropic-version']) {
+      req.headers['anthropic-version'] = '2023-06-01'
+    }
+    
+    if (!req.headers['anthropic-dangerous-direct-browser-access']) {
+      req.headers['anthropic-dangerous-direct-browser-access'] = 'true'
+    }
+    
+    logger.api(`🔧 Browser fallback activated for ${isChromeExtension ? 'Chrome extension' : 'browser'} request`)
+    logger.api(`   Original User-Agent: "${req.originalUserAgent}"`)
+    logger.api(`   Origin: "${origin}"`)
+    logger.api(`   Modified User-Agent: "${req.headers['user-agent']}"`)
+  }
+  
+  next()
+}
+
+module.exports = {
+  browserFallbackMiddleware
+}