Store failed activities

If the processing for an activity failed due to internal reasons (NOT
malformed content), store it for a later attempt

web/public/api/activitypub/inboxUndo.go

@@ -12,7 +12,7 @@ import (
 	"git.mstar.dev/mstar/linstrom/storage-new/dbgen"
 )
 
-func handleUndo(w http.ResponseWriter, r *http.Request, object map[string]any) {
+func handleUndo(w http.ResponseWriter, r *http.Request, object map[string]any) bool {
 	log := hlog.FromRequest(r)
 	_ = object["id"].(string)
 	_, ok := object["actor"].(string)