feat: add HEIC/HEIF image format support

Add detection, MIME type mapping, and dimension parsing for HEIC/HEIF
images via ISOBMFF ftyp brand inspection and ispe box parsing. Update
Gemini relay to accept these formats and refactor getImageConfig to
properly retry decoders using buffered data.

service/image.go

@@ -159,20 +159,36 @@ func DecodeUrlImageData(imageUrl string) (image.Config, string, error) {
 }
 
 func getImageConfig(reader io.Reader) (image.Config, string, error) {
+	// Read all data so we can retry with different decoders
+	data, readErr := io.ReadAll(reader)
+	if readErr != nil {
+		return image.Config{}, "", fmt.Errorf("failed to read image data: %w", readErr)
+	}
+
 	// 读取图片的头部信息来获取图片尺寸
-	config, format, err := image.DecodeConfig(reader)
-	if err != nil {
-		err = errors.New(fmt.Sprintf("fail to decode image config(gif, jpg, png): %s", err.Error()))
-		common.SysLog(err.Error())
-		config, err = webp.DecodeConfig(reader)
-		if err != nil {
-			err = errors.New(fmt.Sprintf("fail to decode image config(webp): %s", err.Error()))
-			common.SysLog(err.Error())
+	config, format, err := image.DecodeConfig(bytes.NewReader(data))
+	if err == nil {
+		return config, format, nil
+	}
+	common.SysLog(fmt.Sprintf("fail to decode image config(gif, jpg, png): %s", err.Error()))
+
+	config, err = webp.DecodeConfig(bytes.NewReader(data))
+	if err == nil {
+		return config, "webp", nil
+	}
+	common.SysLog(fmt.Sprintf("fail to decode image config(webp): %s", err.Error()))
+
+	// Try HEIF/HEIC: parse ISOBMFF ispe box for dimensions
+	if heifMime := detectHEIF(data); heifMime != "" {
+		formatName := "heif"
+		if heifMime == "image/heic" {
+			formatName = "heic"
 		}
-		format = "webp"
+		if w, h, ok := parseHEIFDimensions(data); ok {
+			return image.Config{Width: w, Height: h}, formatName, nil
+		}
+		return image.Config{}, "", fmt.Errorf("failed to decode HEIF/HEIC image dimensions")
 	}
-	if err != nil {
-		return image.Config{}, "", err
-	}
-	return config, format, nil
+
+	return image.Config{}, "", err
 }