feat(release): migrate GeekAI v4.3.0 to open source

- Sync backend and frontend from GeekAI Plus v4.3.0

- Remove commercial License flows and update open-source deployment defaults

- Preserve Docker Compose deployment and bump image tags to v4.3.0

BREAKING CHANGE: commercial License configuration and related endpoints are removed

api/service/ppt/reference_image.go

@@ -0,0 +1,50 @@
+package ppt
+
+import (
+	"encoding/base64"
+	"fmt"
+	"geekai/core/types"
+	"net/http"
+	"net/url"
+	"os"
+	"strings"
+)
+
+// PrepareReferenceInputsForImg2Img 将幻灯片参考图转为第三方 API 可消费的输入：本地存储时读文件并转为 data URI（base64），公网 URL 原样传递。
+func PrepareReferenceInputsForImg2Img(rawURL string, oss types.OSSConfig, app *types.AppConfig) ([]string, error) {
+	rawURL = strings.TrimSpace(rawURL)
+	if rawURL == "" {
+		return nil, fmt.Errorf("empty reference image url")
+	}
+	if strings.HasPrefix(rawURL, "data:") {
+		return []string{rawURL}, nil
+	}
+
+	if oss.Active == "local" {
+		if fp, ok := mapLocalUploadFile(rawURL, oss.Local); ok {
+			b, err := os.ReadFile(fp)
+			if err != nil {
+				return nil, fmt.Errorf("read local reference image: %w", err)
+			}
+			if _, err := decodeImageBytes(b); err != nil {
+				return nil, fmt.Errorf("reference is not a valid image: %w", err)
+			}
+			mime := http.DetectContentType(b)
+			if !strings.HasPrefix(mime, "image/") {
+				mime = "image/png"
+			}
+			dataURI := fmt.Sprintf("data:%s;base64,%s", mime, base64.StdEncoding.EncodeToString(b))
+			return []string{dataURI}, nil
+		}
+	}
+
+	if u, err := url.Parse(rawURL); err == nil && u.Scheme != "" && u.Host != "" {
+		return []string{rawURL}, nil
+	}
+
+	abs := resolveAbsoluteImageURL(rawURL, oss.Local, app)
+	if strings.TrimSpace(abs) == "" {
+		return nil, fmt.Errorf("cannot resolve reference image url")
+	}
+	return []string{abs}, nil
+}