Support repacking tables with referring foreign keys in non-default schemas

[Bouallegui-Moudhaffer]

Psycopack already tracks referring FK schema metadata, but repacking currently rejects referring foreign keys outside the target table’s schema.

Proposed scope for this PR:

• allow referring FKs from other schemas
• preserve constraint validation state
• keep ownership / privilege checks explicit
• add regression tests for a table in public referenced from another schema
• support both DIRECT_TRIGGER and CHANGE_LOG

Non-goals:

• changing behavior for referred FKs
• partitioning or broader schema-management features