fix: explicitly cache images to prevent unexpected behavior

backend/internal/controller/oidc_controller.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"net/url"
 	"strings"
+	"time"
 
 	"github.com/gin-gonic/gin"
 
@@ -545,6 +546,8 @@ func (oc *OidcController) getClientLogoHandler(c *gin.Context) {
 		return
 	}
 
+	utils.SetCacheControlHeader(c, 15*time.Minute, 12*time.Hour)
+
 	c.Header("Content-Type", mimeType)
 	c.File(imagePath)
 }