Explicitly set workspaceId column as uuid type to ease pg LEFT JOIN (#15430)

Pg scan was redundant because historically the workspaceId was
`varchar`, even though below migration won't change that we had a look
to workspaceId col declaration across the codebase

packages/twenty-server/src/engine/core-modules/app-token/app-token.entity.ts

@@ -52,8 +52,8 @@ export class AppTokenEntity {
   @JoinColumn({ name: 'workspaceId' })
   workspace: Relation<WorkspaceEntity>;
 
-  @Column({ nullable: true })
-  workspaceId: string;
+  @Column({ nullable: true, type: 'uuid' })
+  workspaceId: string | null;
 
   @Field()
   @Column({ nullable: false, type: 'text', default: AppTokenType.RefreshToken })