feat: migrate one-time and signup tokens to an actor (#1611)

Co-authored-by: Elias Schneider <login@eliasschneider.com>

backend/internal/model/one_time_access_token.go

@@ -1,13 +0,0 @@
-package model
-
-import datatype "github.com/pocket-id/pocket-id/backend/internal/model/types"
-
-type OneTimeAccessToken struct {
-	Base
-	Token       string
-	DeviceToken *string
-	ExpiresAt   datatype.DateTime
-
-	UserID string
-	User   User
-}