refactor: rewrite form pages using form helper

• add installGateway property 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 from auth forms for better ux
• rename pub_date field to published_at and add publication time in episode form

closes #14 (closed), #28 (closed)