feat: add default label template setting and apply it to print dialog selection

paperless-backend/src/database/entities/user-settings.entity.ts

@@ -28,4 +28,7 @@ export class UserSettings {
 
   @Column({ type: 'text', nullable: true })
   MailSignatureHtml!: string | null;
+
+  @Column({ type: 'int', nullable: true })
+  DefaultLabelTemplateId!: number | null;
 }