add openai pdf upload support

db/migrate/20250804110000_add_pdf_support_to_captain_documents.rb

@@ -0,0 +1,8 @@
+class AddPdfSupportToCaptainDocuments < ActiveRecord::Migration[7.1]
+  def change
+    add_column :captain_documents, :content_type, :string
+    add_column :captain_documents, :file_size, :bigint
+    
+    add_index :captain_documents, :content_type
+  end
+end