Add migration to fix peminjaman.id_buku foreign key: modify column to INT UNSIGNED and re-create FK referencing buku.id_buku with cascadeOnDelete. Update admin peminjaman blades to use $b->id_buku for option values. Remove unused imports and tidy up formatting/whitespace in Peminjaman and AdminPeminjaman controllers (including small reformat of Fonnte API payload). These changes ensure the dropdowns use the correct book identifier and the DB relation is consistent.