feat: init sproutclaw-web — Go+Gin backend + React frontend

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/services/images.go

@@ -0,0 +1,42 @@
+package services
+
+import (
+	"encoding/base64"
+	"fmt"
+	"strings"
+
+	"sproutclaw-web/internal/models"
+)
+
+const (
+	maxImages    = 8
+	maxImageSize = 10 * 1024 * 1024 // 10 MB
+)
+
+var allowedImageTypes = map[string]bool{
+	"image/jpeg": true,
+	"image/png":  true,
+	"image/gif":  true,
+	"image/webp": true,
+}
+
+// ValidateImages checks image count, type, and base64-decoded size.
+func ValidateImages(images []models.ChatImage) error {
+	if len(images) > maxImages {
+		return fmt.Errorf("最多支持 %d 张图片，当前 %d 张", maxImages, len(images))
+	}
+	for i, img := range images {
+		mt := strings.ToLower(img.MediaType)
+		if !allowedImageTypes[mt] {
+			return fmt.Errorf("图片 %d 类型不支持: %s", i+1, img.MediaType)
+		}
+		decoded, err := base64.StdEncoding.DecodeString(img.Data)
+		if err != nil {
+			return fmt.Errorf("图片 %d base64 解码失败", i+1)
+		}
+		if len(decoded) > maxImageSize {
+			return fmt.Errorf("图片 %d 超过 10MB 限制", i+1)
+		}
+	}
+	return nil
+}