refactor: rewrite form pages using form helper

- add installGateway to app config
- update route names and groups
- remove `author_name` and `author_email` from `episodes` table
- remove `author_name` and `author_email` from `podcasts` table
- remove `owner_id` + add `created_by` and `updated_by` fields in `podcasts` and `episodes` tables
- remove unnecessary comments in database fields
- remove confirm password inputs from auth forms for better ux
- rename `pub_date` field to `published_at` and add publication time field in episode form

closes #14, #28