feat: add multi-file type support for Gemini and Claude

- Add file data DTO for structured file handling
- Implement file decoder service
- Update Claude and Gemini relay channels to handle various file types
- Reorganize worker service to cf_worker for clarity
- Update token counter and image service for new file types

constant/env.go

@@ -10,6 +10,8 @@ import (
 var StreamingTimeout = common.GetEnvOrDefault("STREAMING_TIMEOUT", 60)
 var DifyDebug = common.GetEnvOrDefaultBool("DIFY_DEBUG", true)
 
+var MaxFileDownloadMB = common.GetEnvOrDefault("MAX_FILE_DOWNLOAD_MB", 20)
+
 // ForceStreamOption 覆盖请求参数，强制返回usage信息
 var ForceStreamOption = common.GetEnvOrDefaultBool("FORCE_STREAM_OPTION", true)