Fixes intermittent NULL mediaId foreign key on media_request records byadding explicit @JoinColumn
decorator to the media relation. Without this,TypeORM's implicit FK mapping was unreliable, causing
orphaned requeststhat would crash the frontend when accessing user profiles. Also removes the
redundant @Column decorator for mediaId which conflicted withthe relation, and removes explicit
mediaId assignments in the constructorwhich are now handled correctly by TypeORM through the
relation.