refactor(file-source): unify file source creation and enhance caching mechanisms

service/token_counter.go

@@ -100,8 +100,6 @@ func getImageToken(c *gin.Context, fileMeta *types.FileMeta, model string, strea
 	if err != nil {
 		return 0, err
 	}
-	fileMeta.MimeType = format
-
 	if config.Width == 0 || config.Height == 0 {
 		// not an image, but might be a valid file
 		if format != "" {
@@ -268,7 +266,6 @@ func EstimateRequestToken(c *gin.Context, meta *types.TokenCountMeta, info *rela
 				}
 				continue
 			}
-			file.MimeType = cachedData.MimeType
 			file.FileType = DetectFileType(cachedData.MimeType)
 		}
 	}