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

service/file_decoder.go

@@ -0,0 +1,39 @@
+package service
+
+import (
+	"encoding/base64"
+	"fmt"
+	"io"
+	"one-api/constant"
+	"one-api/dto"
+)
+
+var maxFileSize = constant.MaxFileDownloadMB * 1024 * 1024
+
+func GetFileBase64FromUrl(url string) (*dto.LocalFileData, error) {
+	resp, err := DoDownloadRequest(url)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	// Always use LimitReader to prevent oversized downloads
+	fileBytes, err := io.ReadAll(io.LimitReader(resp.Body, int64(maxFileSize+1)))
+	if err != nil {
+		return nil, err
+	}
+
+	// Check actual size after reading
+	if len(fileBytes) > maxFileSize {
+		return nil, fmt.Errorf("file size exceeds maximum allowed size: %dMB", constant.MaxFileDownloadMB)
+	}
+
+	// Convert to base64
+	base64Data := base64.StdEncoding.EncodeToString(fileBytes)
+
+	return &dto.LocalFileData{
+		Base64Data: base64Data,
+		MimeType:   resp.Header.Get("Content-Type"),
+		Size:       int64(len(fileBytes)),
+	}, nil
+}