fix errors in migration scripts

kontor-rails/db/migrate/20250626095145_create_publishers.rb

@@ -6,7 +6,7 @@ class CreatePublishers < ActiveRecord::Migration[8.0]
       t.integer :version
       t.string :name
       t.string :weblink
-      t.belongs_to :publisher, optional: true
+      t.string :parent_publisher_id
     end
     change_column :publishers, :id, :string
   end

kontor-rails/db/migrate/20250626095203_create_comics.rb

@@ -8,7 +8,7 @@ class CreateComics < ActiveRecord::Migration[8.0]
       t.boolean :current_order
       t.boolean :completed
       t.string :weblink
-      t.belongs_to :publisher, foreign_key: true
+      t.belongs_to :publisher
     end
     change_column :comics, :id, :string
   end

kontor-rails/db/migrate/20250626095943_create_issues.rb

@@ -9,9 +9,9 @@ class CreateIssues < ActiveRecord::Migration[8.0]
       t.datetime :published_on
       t.boolean :in_stock
       t.boolean :is_read
-      t.belongs_to :comic, foreign_key: true
-      t.belongs_to :volume, foreign_key: true
-      t.belongs_to :story_arc, foreign_key: true
+      t.belongs_to :comic
+      t.belongs_to :volume
+      t.belongs_to :story_arc
     end
     change_column :issues, :id, :string
   end