Grant Wizard does not grant priviledges to a schema

Describe the solution you'd like

In the Grant Wizard of pgAdmin 4, when selecting all objects within a schema (e.g., all tables, sequences, etc.), I would expect the wizard to also grant privileges on the schema itself. Currently, privileges are granted only to the individual objects within the schema, but not to the schema itself. As a result, users may still encounter permission errors such as "permission denied for schema X" even after using the wizard to grant "ALL" privileges on all objects.

It would be helpful if the wizard could optionally include the schema-level privileges (e.g., USAGE) when granting permissions on all objects within a schema.

Describe alternatives you've considered

I have manually executed GRANT USAGE ON SCHEMA ... TO ... as a workaround, but this defeats the purpose of using the wizard for convenience and completeness. There is currently no option in the wizard UI to include schema-level privileges when granting permissions on contained objects.

Additional context

This behavior may be surprising to users who assume that "all objects" includes the schema itself. Improving this would make the permission granting process more intuitive and reduce confusion for administrators.

Example error after using the wizard:

ERROR: permission denied for schema gate
LINE 1: SELECT count(*) FROM gate.table;

Start with the Grant Wizard flow described in the issue and reproduce granting privileges on all objects within a schema. Trace how the wizard generates grants and determine where schema-level privileges can be included. Done means the wizard can grant the needed schema privilege, such as USAGE, and the reported permission error no longer occurs.